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Accessories
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Accessories

A . Ampere or amp. The unit measure of electrical current.

AC . Alternating Current or the varying amplitude characteristic of an electrical signal. All information-carrying signals, including audio signals, are AC, as it is the signal's variation that contains the information.

Active . As in an active rather than passive circuit. Generally denotes a circuit that operates from an electrical power source such as the AC line or batteries. For example, active circuits include amplifiers, receivers and CD players. In contrast, passive circuits like most speakers and headphones require no source of electrical power but rely solely upon the electrical audio signal for operation.

Active Speaker . A speaker having an internal power amplifier for increased speaker drive. This contrasts with the more typical speaker which derives its operating power solely from the audio signal supplied to it. Active speakers most often appear as active subwoofers where an internal power amplifier boosts the speaker's drive signal.

AES-EBU . The Audio Engineering Society and European Broadcasting Union connection standard often employing XLR connectors.

Anodized . Having a metal oxide finish as opposed to paint. An anodized finish is formed by an electrolytic process in which the object to be coated serves as the anode, hence the term anodized. Anodizing produces a durable semi-translucent finish in a wide range of colors with black and gold being common in audio equipment.

A/V . Audio/Video.

AWG. American wire gauge standard for wire diameter classification.

Banana Plug . A single-wire plug having expanded metal contacts that provide spring tension when inserted into a mating banana jack. Provides quick connection ease and is particularly useful in applications requiring frequent change. Generally the simplest interconnect solution, however, somewhat less reliable than the lock-down connection of a binding post.

Bandpass . Passing a specific band of frequencies defined by upper and lower cutoffs. In equalizers, bandpass filters commonly separate an audio signal into multiple frequency ranges for separate control of response characteristics within the various ranges.

Bandwidth . A frequency range of response most commonly defined by an upper frequency limit. Bandpass responses, such as those of speakers and equalizers, are defined by both upper and lower limits.

Binding Post . A versatile connector jack that accepts banana plugs and provides screw-down wire connection for either wire lugs or a thru-shaft wire insert. Typically located on the backs of speakers or amplifiers.

Capacitor . An electronic component that presents a frequency dependent impedance which decreases in proportion to frequency. Commonly used to shunt unwanted high-frequency signals or to block the coupling of DC voltages.

Car Cord . Adapter cord for power supply from a car cigarette lighter socket to a portable electronic device.

CCAW . Copper-Clad Aluminum Wire

Center Frequency . The midpoint frequency of a filter response. That frequency most commonly specified to denote a bandpass or band reject filter.

CM. Common-Mode . Common to the two lines of an electrical connection. Coupled noise often occurs as a common-mode signal on the two line of a differential connection. Common-mode rejection removes such error signals without disturbing the desired differential signal.

COAX . Coaxial; having a common center axis as with the two conductors of a coax cable or coax connector.

COAX Cable . A cable having two coaxial conductors with the outer conductor serving as an electrical noise shield for the inner one. The best solution for coupling low-level antenna or dish signals to TV sets and VCRs. Requires the installation of COAX connectors at the ends of each cable run.

Compander . A signal dynamic range compressor/expander; often used for noise sensitivity reduction. Compressing the dynamic range increases the magnitudes of the lower level signals, which are the ones most sensitive to noise error. Recorded in this form, signals remain less sensitive to tape noise. Re-expanding the dynamic range later restores the signal in the absence of that noise source.

Compress Ratio . The degree of signal compression produced by a limiter. Ideally this ratio would be infinite to totally block signal transmission above the limit threshold. However, practical constraints restrict this compression to around 20:1.

Constant-Q Response . Having constant selectivity (response sharpness). One of several responses achieved with bandpass filters, the constant-Q alternative typically provides a flatter overall response in the passband.

Converter (Power). Converts an input power line voltage to a different output power line voltage. In a frequent application, such a converter reduces the 240V line output common in Europe to the 120V common in the U.S. This conversion permits the operation of electronic products intended for the U.S. from European power sources.

dB (decibel). A logarithmic unit of relative signal level. For signal power, P(dB) = 10log(P1/P2) represents the power level P1 as compared with reference level P2. Differs from dBu in that the latter is referenced to a reference P2 level of 0.775Vrms.

dB/Octave (dB/Oct). Frequency response roll off rate or slope. This slope reflects the selectivity or response sharpness of equalizer passbands. 6 dB/octave represents the basic single-pole response roll off and 18 dB/octave represents a highly selective, three-pole response characteristic.

dBu . The dB signal level relative to a reference level of 0.775 Vrms. [dBu = 20log(es/0.775).] Differs from dB in that the latter only provides a relative measure of two arbitrary signal levels.

DB-9 . A 9-pin, D-connector configuration frequently used for computer equipment interconnections like those required for computer control of audio signals.

DB-25 . A 25-pin, D-connector configuration frequently used for computer equipment interconnections like those required for computer control of audio signals.

DC . Direct Current or zero frequency, reflecting a voltage or current that does not vary with time like an AC signal. Batteries supply DC signals while audio signals are AC.

DIN . (Deutsche Industrie Norman) A German standard that defines mechanical configurations such as those of some older European audio connectors.

Directivity (Microphone). Response pattern. Expresses the geometric shape of the region of sensitivity surrounding the microphone in terms such as omnidirectional or cardiod. A narrow directivity like cardiod better separates a desired sound signal from background noise as generally desired in single voice use. A wide directivity like omnidirectional best serves applications involving multiple sound sources at varied locations, such as those produced by an orchestra.

DRAM . Dynamic Random Access Memory.

EQ . ( See Equalizer)

Equalizer . A multi-band audio bandpass filter having individual gain or attenuation controls for each band. Adjusting the controls shapes the overall frequency response to add emphasis or reduction of various signal frequencies, controlling the character of the overall sound result. Essentially a multi-band tone control.

Filter . An electronic circuit that selectively separates a band of signal frequencies, such as a low-pass filter for the separation of the low-frequency components of an audio signal. Filters serve as the basic element of equalizers where multiple filter channels permit frequency response tailoring.

Filter Slope . The response roll-off rate outside the filter passband. The greater the roll off, the higher the filter selectivity. Crossover networks commonly provide 18 dB/octave response roll offs for a high degree of discrimination between adjacent frequency bands.

Freq. Frequency.

Frequency . The rate of repetition of a signal in cycles per second. Higher audio frequencies correspond to treble tones and lower ones correspond to bass. Radio frequencies define station locations within a broadcast band.

Frequency Range . A range of frequencies between high and low end points. A passband or bandwidth. Individual speaker elements like woofers, midranges and tweeters serve different frequency ranges within the overall audio frequency range. (See also Frequency Response.)

Frequency Response . The range of signal frequencies supplied by an amplifier or reproduced by a speaker or microphone, as specified by the upper and lower bounds of the frequency range in Hertz (Hz). Typically, 20Hz to 20kHz encompasses the full range of human hearing and separate audio speakers generally serve different segments of this range.

F-type connector . An economical coaxial connector commonly used for TV antenna or cable connections.

g . Gram(s). A metric unit of weight. (Approximately .035 ounces)

GHz ( Gigahertz). A measure of signal frequency expressing thousands of million cycles per second.

Hi&lo Pass . High and low pass, as in speaker crossover networks. Frequency response bands separated by the high-pass and low-pass filters of tone controls and equalizers to isolate treble and bass signals for separate control. (See also High Pass and Low Pass.)

High Pass . Passing only higher frequencies, such as the high-pass filters that provide treble control in audio equipment. Crossover networks and equalizers also incorporate high-pass filters to separate or control the treble component of audio signals.

Hi-lo or Hi/Lo . High-low. (See also Hi&lo Pass, High Pass and Low Pass.)

Hipass . ( See High Pass)

HP. ( See High Pass)

HPF . High-pass filter. ( See High Pass)

Hz (Hertz) . A measure of signal frequency expressing signal cycles per second. (The audio frequency range extends from 20Hz to 20kHz where 20kHz = 20,000Hz.)

Impedance . The electrical characteristic of an electronic device that reflects the voltage developed in response to a current supplied to the device. High impedance receiver inputs respond with less power demand upon a received input signal. Low impedance speakers permit higher power drive from a given amplifier output voltage.

Insertion Loss . Signal loss as a result of the insertion of an element in a line.

Inverter . A power converter; as commonly used to derive line-power backup from batteries. Inverters chop a battery's DC output voltage into time varying segments to produce an AC power signal.

Isolation Transformer . A transformer used to break hum producing ground loops by permitting different input and output ground references. This isolation interrupts ground current paths that could otherwise couple ground reference differences into the signal path.

KVA (Kilovolt-Amp). An electrical power-rating product of voltage and current, as specified for an uninterruptable power source. Dividing that product by the line voltage, (110V in the USA, 220V in Europe) yields the output current rating of the power source.

LAN . Local Area Network. A computer interconnection network for limited connection distances, like those of an office environment.

Lavaliere Design (Microphone) . Clip-on; as with a lapel mic.

Low Cut . The low-frequency cutoff of an AC response. Attenuates signals having frequencies below that of the low cutoff. The opposite of Low Pass. Low cut filters, for example, remove bass signals from the tweeter drive.

Low Pass . Passing lower frequencies, such as the low-pass filter that provides bass control in audio equipment. In that application, the filter separates the bass components from the audio signal for separate volume control. The opposite of Low Cut. Analogous to the High Pass filters used to separate high frequency audio signals for treble control.

m . Meter

mA . (Milliamp). 0.001 amp.

Magnetic Shielding . Electrical shielding against electromagnetic interference such as that commonly produced by transformers. Commonly achieved with high permeability metallic shields that intercept and conduct electromagneticly coupled signals to ground.

MB . Megabit; one million bits of digital information.

Metal Particle Tape . Audio/Video tape having a metal particle layer for improved high-frequency response. The high permeability of the metal particles used to coat such tape permits reducing the particle size to extend frequency response.

MHz. (Megahertz). A measure of signal frequency expressing millions of cycles per second.

Mixer . An audio or video processor that combines two or more source signals in an output signal. Separate controls typically permit tone and volume control over the contribution of each source signal to achieve an optimum tone balance.

mm . Millimeter(s). (Approximately .04 inches; 1" = 25.4mm)

Modular . Contained in a variety of separate enclosures or cases as opposed to within one common enclosure. Modular audio systems typically consist of separately cased signal sources, amplifiers and speakers.

Modulator (Video/Audio). An electronic signal processor that combines a video/audio signal with a carrier signal for distribution. A later demodulator removes the carrier following transmission to restore the original signal. Analogous to radio transmission.

mV . (Millivolt). 0.001 volt.

NM . Normal-Mode. Between the two lines of an electrical connection. Typically the desired signal of a two-wire coupling. The converse of common-mode.

OFC . Oxygen-Free Copper. Purified to provide lower line resistance for reduced parasitic line drops.

Ohm . The unit of electrical impedance, equaling an element’s voltage drop divided by its associated current.

Omnidirectional Pickup. Responsive in all directions as with omnidirectional microphones that respond to sound input from any direction as opposed to directional microphones. ( See also Polar Pattern.)

PA . Public Address.

Panhead . The position-adjustable mounting head of a photographic tripod. Permits free-moving left-to-right and/or up-down rotation or panning of a mounted camera.

PCM . Pulse-Code Modulation. Signal encoding through modulation of a carrier pulse width. A signal encoding technique used in digital audio and some switching power supplies.

Peak Limiters . Signal amplitude limiters that clip or terminate response at higher signal levels beginning at a limit threshold. Used to prevent overdrive conditions.

Polar Pattern . The spatial responsivity pattern of a microphone. This describes the shape of the region surrounding the microphone that produces the greatest response. Different microphone designs respond to different patterns for different applications. For example, cardiod patterns provide very directional responses suitable for selectively receiving a single audio input. Omnidirectional patterns capture sound from all directions to detect surrounding sounds as well.

Power Inverter . A DC-to-AC power converter for powering AC devices from a battery source. These inverters transform a DC input voltage into an AC output voltage capable of powering devices designed for line power operation. Often used as a computer's uninterruptable power source or UPS. Typically restricted in output power capability to short duration demands.

PVC . PolyVinyl Chloride; a flexible plastic often used for wire insulation.

PWR . Power.

Q Control . Response selectivity control. Varies the roll-off sharpness of a filter passband to control the selectivity of the band.

RCA Inputs/Outputs . Signal connections presented with RCA connectors. Economical, plug-in coaxial connections for audio and component video applications.

Regulated . Controlled or stabilized, as in a power supply output that remains insensitive to the varying load demands produced by signal variations. Power supply regulation is typically specified as the percentage variation in rated output voltage produced by regulation error in conjunction with a specified load current demand.

Release Time . The time required to deactivate a limiter following a signal return to levels below the limit threshold. During this time, signal coupling through the limiter remains blocked, making short release times desirable.

RJ-11 connector . The modular phone jack/plug commonly used at the two ends of telephone cords and also used for modem, FAX and other computer peripheral connections.

RMS . Root-Mean-Square . An amplitude measure of an electrical signal that reflects the net power capability of the signal or a speaker. Note that this differs from the peak power, which reflects the maximum instantaneous power capability.

Screw Terminal . A wire connection terminal having a center screw for compressing a bare wire end against a flat metal contact. Used for speaker wire and antenna lead connections. Sometimes grouped in the multiple terminals of a barrier strip.

Shielded Cable . A cable having an outer shield conductor that often serves as the ground return. That outer conductor absorbs coupled interference signals to shield the inner signal-carrying conductor from such interference.

SLIC . Subscriber-Loop-Interface-Circuit. A telephone line interface.

SMT . Surface Mount Technology. A high-density electronic component mounting alternative used for compactness and automated assembly economies. Installed surface mounted devices are easily recognized by their wireless, direct solder connections to a printed circuit board.

Spike Protection . Power-line transient suppression that dissipates voltage spikes to protect line powered equipment. Surge suppressors most commonly provide this protection by shunting over-voltage transients. Commonly used to intercept lightning induced spikes.

Splitter (RF). A signal divider that splits an incoming signal into multiple output signals, such as required to supply multiple TV sets from a common antenna. Without the impedance balancing provided by a splitter, the supply of multiple loads from a common antenna compromises signal strength. In doing so, splitters reduce the signal power available to each output. As a result, a distribution amplifier may be a better solution for a larger number of receivers or for weaker signal conditions.

Step-Down Converter . Converts a power line voltage to a lower level such as 240V-to-120V. Commonly used for the operation of electrical/electronic devices in countries having the higher 240V power systems. Often incorporated within electronic equipment and activated thru a rear-panel 120V/240V switch.

Surge . A temporary high-current power line demand often developed during system turn on. The system's line power source must be capable of supplying this temporary current without tripping a circuit breaker. For audio equipment the surge current demand will not likely be sufficient to trip a circuit breaker except with very large equipment installations.

Surge Current . That current drawn during the surge condition; typically a turn-on event.

Talkover . A signal mixing application generally combining a vocal input with a background playback. Typically, the vocal input is real time and supplied by a microphone while the background is supplied from a recorded source, as in Karaoke applications.

TBC. Time Base Corrector.

Terminal . A wire or cable connection point, as generally supplied by a cable mating connector, banana jack or wire clamp.

THD . Total Harmonic Distortion. A measure of the distortion content of a signal as represented by equivalent harmonics of that signal and specified as a percentage of the signal amplitude. While the equivalent harmonics represented do not actually exist in the signal, their summation would reproduce the distortion component of the signal. Further, filter separation of the signal into its fundamental and harmonic frequencies yields the harmonics for identification and measurement comparison with the fundamental.

Twisted Pair . A two-wire cable that reduces coupled noise effects by making them a common-mode signal. Twisting the two wires equalizes their average distances from radiating noise sources to equalize the noise pick up of the two. Noise common to the two wires does not affect the differential coupling of the desired signal. Without the twisted configuration, differing separation distances between the noise sources and the two wires would result in unequal noise coupling that would add to the intended signal.

UHF . Ultra-High-Frequency. A television broadcast frequency band above the more common VHF band.

UL . Underwriters Laboratory. A private institution that tests and rates electrical/electronic products for safety. Generally applicable to AC operated equipment and indicated by product labeling when certified.

Unidirectional Microphone . One that responds to direct axis sound but remains insensitive to off-axis sound and background noise. The unidirectional response is well suited to the reception of a single voice or instrument sound but not to multi-source sound combinations. Multi-source requirements are better served by an omnidirectional microphone that responds to sounds from all directions.

UPS . Uninterruptable Power Source. Battery-powered back-up for an AC line supply like that commonly used with personal computers. Such sources have a VA (Volt-Amp) power rating that defines the supply capability. Dividing that rating by the power line voltage of the equipment to be powered (110V or 220V) yields the supply current capability.

V . Volt. The unit measure of electrical voltage.

VA . Volt-Amp. A power rating product specified for an uninterruptable power source. Dividing this product by the voltage supplied, usually 110V, yields the current supply available.

VAC . Volts, AC.

VDC . Volts, DC.

VHF . Very-High-Frequency. A broadcast frequency band.

Vp-p . Volts Peak-to-Peak.

Vrms . Volts, root-mean-square. A time averaged measure of an AC voltage signal that more directly reflects the power delivery potential of the signal.

W (Watt). A unit measure of electrical power equaling the product of voltage and current.

Wh or WH . Watt-hour; a power-time product that reflects energy potential or consumption.

Amplifiers

A . Ampere or amp. The unit measure of electrical current.

A/B Inputs . Two input connections under the control of an A/B switch. Such switches permit the selection of either of two sources, such as tape or receiver signals, for a given amplifier input signal.

A/B Switch. A two-pole selector switch permitting signal coupling from either of two or devices (A or B) to a common device, such as from multiple audio sources to a given speaker system.

Attenuation . Reduction, as in audio volume control. The converse of amplification. Typically performed with a gain control potentiometer in amplifiers or with a switchable-tap transformer for in-wall volume controls.

Autotransformer . A transformer having a feedback winding for improved signal transfer accuracy, especially at higher power levels. When used in audio power amplifiers, autotransformers greatly reduce the distortion otherwise introduced by output transformer nonlinearities. Rarely required except for the highest of output power levels.

AUX Input . Auxiliary input to an amplifier for the addition of another signal source such as a second tape deck or turntable.

Bass . The lower frequency range of the audio sound spectrum (drums, explosions, etc.) spanning the frequency range of around 20 Hz to 200 Hz. Primarily reproduced by woofers and subwoofers in audio systems.

Bass Boost . Increased bass response for greater low-frequency sound. Often found in headphones where space restrictions limit the internal speaker size, restricting bass response.

Bipolar . Bipolar junction transistor, as often used in the power output stages of audio amplifiers for its superior high-power efficiency.

Boost . Signal gain generally supplied within a selected band of frequencies. Often applied in audio to compensate for restricted bass response, as encountered with headphones, or simply to accentuate bass response.

Bridgeable (Output). An amplifier output capable of driving loads such as speakers that are connected in bridge configurations. Requires two output connections to the load for each bridge drive. (See also Bridged Power).

Bridged Power . The output power of an amplifier when driving a speaker connected in a bridged, as opposed to grounded, configuration. Bridged drive of a speaker potentially quadruples the power drive to the speaker.

Center Channel . An audio sound channel derived from the combined signals of the left and right channels for greater surround effect. A center channel fills in the sound presence between left and right.

CH. ( See Channel)

Channel . One signal path, such as one of the two composing a stereo signal or one of the three containing the bass, midrange and treble segments of an audio signal. Also, a broadcast frequency as in TV and CB transmission.

Channel Separation . Signal isolation between channels such as between the two channels of a stereo system. Greater separation adds depth and spatial sense to audio playback.

Class A Operation . Transistor operation with continuous bias under all load and signal conditions for low distortion and greater bandwidth. While less power efficient, this operating mode avoids the transistor turn-off distortion introduced by the more efficient Class B operation. The reduced distortion of Class A operation most often benefits amplifier output stages. There, wide ranging current demands would routinely exercise the turn-off distortion of Class B bias.

Clipping . A form of distortion in which an amplifier limits or clips signal peaks. Commonly occurs when an amplifier is overdriven beyond its rated output level, resulting in output swing up to limit imposed by the power supply voltage. Results is severe audible distortion.

Continuous Adjustment . A continuously variable or linear adjustment, like that of a potentiometer, as opposed to the discrete step adjustments of a switch. The continuous adjustment typically provides greater adjustment resolution since switched adjustments remain limited by the number of switch positions practical.

Cut . Signal attenuation applied within a selected frequency range. An equalizer tuning function much like a bass or treble control but spanning a more selective frequency range. The opposite of Boost.

Current Feedback . A signal control technique that reduces distortion by sensing an output signal current, comparing it with the input signal and supplying gain to correct any distortion difference. The type of control realized with the feedback winding of an autotransformer.

dB (decibel). A logarithmic unit of relative signal level. For signal power, P(dB) = 10log(P1/P2) represents the power level P1 as compared with a reference level P2. Differs from dBu in that the latter is referenced to a reference P2 level of 0.775Vrms.

dBu . The dB signal level relative to a reference level of 0.775 Vrms. [dBu = 20log(es/0.775).] Differs from dB in that the latter only provides a relative measure of two arbitrary signal levels.

D-Bass . Dynamic bass. A boosted bass response producing increased low-frequency content for greater woofer output. Produces a more dynamic and encompassing sound for action videos. (See also Bass Boost.)

Discrete Output . Output stage(s) formed with individual discrete transistors. For the higher-power output stages of amplifiers, discrete transistors provide greater power handling and more performance alternatives than those included in integrated circuit components.

Distortion . Signal wave shape deviation from the original. To some degree, all electronic equipment inherently distorts signals due to non-ideal signal transfer responses. For a given audio element, Total Harmonic Distortion serves as a quantitative measure of such response deviations. (See also THD.)

Distortion, Harmonic . A measure of the distortion content of a signal as represented by equivalent harmonics of that signal and specified as a percentage of the signal amplitude. While the equivalent harmonics represented do not actually exist in the signal, their summation would reproduce the distortion component of the signal. Further, filter separation of the signal into its fundamental and harmonic frequencies yields the harmonics for identification and measurement comparison with the fundamental.

Double-Sided Board . A printed circuit board having components mounted on both of its surfaces for increased compactness. Multi-layer boards increase the number of interconnect planes for even greater compactness.

Dubbing . Adding a second audio signal to a first signal as in sound-on-sound recording. The second signal does not override the first but rather adds to it. Dubbing can, for example, add background music to a vocal dialog.

Dynamic Headroom . The separation between a maximum signal excursion and the maximum allowable. For audio speakers, this defines the separation between the maximum-recommended operating level and that at which excessive sound degradation occurs.

Dynamic Range . The span between minimum and maximum signal levels as determined by noise and power limitations, respectively. The noise reduction of 16 bit DSP potentially expands this range to 96 dB, however, speakers and headphone responses then impose a final limitation.

Dynamic Range Compression . Low-level signal amplification and high-level signal attenuation applied to raise signals well above the background noise level without exceeding maximum amplitude levels. Used to reduce the significance of tape noise. Requires signal re-expansion in the playback process.

EL . Electro-Luminescent. An illuminated display often found in auto radios that employs electro-luminescence rather than an incandescent bulb to light the display.

EMI . Electromagnetic interference. Electrical interference coupled by magnetic fields like the car radio noise sometimes produced by the car's ignition system. Can also result from parasitic coupling from transformers.

Equivalent Input Noise . Output noise divided by the circuit gain. This input representation permits direct comparison of noise and signal levels for qualitative evaluation.

Feedback . Supply of a portion of a circuit's output signal to the circuit input for comparison with the input signal and the generation of an error correction signal. Commonly used to reduce distortion in amplifier stages. The underlying principle of the autotransformers sometimes used in amplifier output stages.

FET . Field effect transistor. A lower-distortion but lower-gain alternative to the bipolar transistor. Often used for higher-power amplifier output stages and higher-impedance receiver input stages. Less effective than bipolar transistors in amplifier gain stages.

Freq. Frequency.

Frequency Response . The range of output signal frequencies supplied by an amplifier, speaker or microphone as specified by the upper and lower bounds of the frequency range in Hertz (Hz). Typically, 20Hz to 20kHz encompasses the full range of human hearing and separate audio speakers generally serve different segments of this range.

Front/Rear Fader . A front-to-rear balance control, as commonly used in car audio systems to achieve volume balance between front- and rear-mounted speakers. This control simultaneously increases volume in one location while reducing it in the other. Analogous to the more common Left/Right balance control of general audio systems.

F&R . Front and Rear, as in car audio volume balance. (See also Front/Rear Fader.)

Gain . Amplification factor. Gain increases signal magnitude for greater sound volume or improved radio and TV reception. Commonly provided by an amplifier in audio or by an antenna in radio and TV.

GND . Ground. The zero reference point from which a voltage or voltages are measured. In the most basic case, earth ground. In electronic systems, generally the chassis or case ground of the system.

Ground Loop. A crosstalk producing condition in which the ground line currents from one signal produce voltage drops that add to a companion signal path. Star connection returns of all grounds at a common point avoid such parasitic interference.

Headroom . The separation between a maximum rated signal excursion and the maximum allowable. For an audio speaker, the power level separation between a continuous operating capability and the higher level for which short term excursions can be handled without damage.

Hz (Hertz). A measure of signal frequency expressing signal cycles per second. (The audio frequency range extends from 20Hz to 20kHz where 20kHz = 20,000Hz.)

Impedance . The electrical characteristic of an electronic device that reflects the voltage developed in response to a current supplied to the device. Speakers typically display a low 4 ohm or 8 ohm input impedance to accept high power drive from reasonably low signal voltages. Microphones typically present a high output impedance to develop a sufficiently high signal voltage from their low internal power generation.(See also Impedance Matching.)

Impedance Matching . Matching a driven load impedance to that of the source for maximum power transfer, as often implemented through transformer coupling for impedance transformation. A feature incorporated in many in-wall volume controls through transformer tap selection. Becomes especially important where multiple speakers share a given audio signal line, as each speaker added alters the net load impedance.

Input Impedance . That impedance presented by the input of an electronic device, as commonly expressed in ohms. Amplifiers typically present high input impedances to limit loading effects on their signal sources. Speakers most commonly present low input impedances to accept higher drive power. Most speakers have an 8 ohm input impedance, although 4 ohm and 16 ohm types exist for different applications.

In/Out . Input/Output.

Isolated Mounting Legs . Equipment support legs that electrically isolate a case from unwanted ground connections that could introduce ground-loop interference.

kHz (kilohertz) . A measure of signal frequency expressing thousands of cycles per second.

kohm (kilo-ohm). A measure of electrical impedance expressing thousands of ohms.

LCD (Liquid Crystal Display). An energy-efficient high-resolution display. Most often produces black characters on a light green background in audio equipment but capable of multi-color.

LED (Light Emitting Diode). A semiconductor diode that generally serves as an electronic indicator light to display the on/off states of equipment functions, usually in red, yellow or green.

Line Input . A high level signal input that bypasses an amplifier's initial gain stage to accommodate line level signals (1 to 2 Vrms). An input that accepts the higher output signal presented by another amplified source.

Line Out (Line Output). An amplifier monitor output that bypasses the amplifier's variable and power gains. This output remains unaffected by volume control variations and free of the distortion introduced by later power stages.

L/R . Left/Right.

mA . (Milliamp). 0.001 amp.

Mic. Microphone.

Milliamp . One thousandth of an amp (.001A).

Mono (Monaural). Monophonic; single-channel audio.

MOSFET. Metal-oxide-semiconductor field-effect-transistor. Often used for higher current or lower distortion in power-driving amplifier stages.

Multi-Channel. Supporting multiple signal paths or channels, such as from an amplifier output to multiple speakers.

mV . (Millivolt). 0.001 volt.

Ohm . The unit of electrical impedance, equaling an element’s voltage drop divided by its associated current.

Optically Isolated . Employing optical isolation between system components to prevent ground loop interference. Particularly effective because the conversion to optical transmission breaks all electrical conduction loops.

Output Impedance . That impedance presented by the output terminals of an electronic device, as commonly expressed in ohms. Lower output impedances facilitate higher power transfer to a load.

PCB. Printed Circuit Board. The board on which electronic components are combined and interconnected to form an electronic circuit.

PCM . Pulse-Code Modulation. Signal encoding through modulation of a carrier pulse width. A signal encoding technique used in digital audio and some switching power supplies.

Phase Shift . Time delay introduced in an electrical signal. Produces phase distortion in audio signals of higher frequencies. Most often the result of amplifier bandwidth limitations.

Phase Shift, Variable . Control over signal phase shift in stereo playback to vary the apparent image location. The associated time delay introduced in one channel of a stereo signal varies the apparent location of sound coincidence or the acoustic image. Phase delay in one channel makes its image further away than that of the other channel to alter the composite image location.

Polarity Switch . An electrical switch included on some amplifiers that permits phase reversal in a speaker drive to check for phase synchronization. Synchronized speaker drive produces additive sound waves while unsynchronized waves tend to produce canceling effects. In the absence of such a switch, simply reversing the wire connections at one speaker produces the same effect but the time required then makes synchronization more difficult.

Power . The amount of electrical energy supplied to or consumed by a device, such as supplied from an amplifier to a speaker or from the power line to the amplifier, as specified in Watts (W).

Power Amplifier . An amplifier dedicated to higher output power levels but typically lacking preamp sensitivity and control functions. Generally used in conjunction with a dedicated preamp to fulfill these other requirements. Such a combination permits largely independent optimizations of input and output features to best serve more sophisticated applications.

Power, Bridged . Power available to a bridge-connected load (speaker). When permitted by the amplifier, the bridge connection of a speaker drives it between two opposing output swings. This drive doubles the speaker's overall voltage swing to potentially quadruple the drive power. Higher impedance speakers in conjunction with higher power amplifiers most likely realize the full bridged-drive benefit. However, amplifier output power limitations may independently restrict this benefit to a drive power doubling, depending upon the specific conditions of the application.

Power, Full-Bandwidth . That power delivered over the entire specified bandwidth. At higher frequencies, amplifier output power generally becomes restricted by a large-signal bandwidth limit that is distinct from the commonly specified small-signal bandwidth. Larger signals encounter a slew rate limit or maximum rate-of-change that imposes this added restriction. However, the amplifier remains capable of delivering the full bandwidth at a reduced power level.

Power Output . The maximum power output available such as from an amplifier output. Higher power output is important for the accurate reproduction of audio signal peaks even if not fully utilized at the average volume level.

Pre-Amp . Pre-Amplifier. A low-level signal amplifier typically used in conjunction with a power amplifier. Pre-amps provide initial signal gain and often include response tuning controls. They are generally capable of driving headphones directly, however, they most often require the addition of a power amplifier for speaker drive.

Punch Bass . Bass boost. Increased low-frequency audio signal drive to accentuate bass components and/or to compensate for restricted low-frequency speaker response. Especially effective with headphones as size restrictions then preclude the use of lower-frequency transducer elements.

PWM Power Supply . Pulse-width modulated power supply for high power efficiency. A type of switching power supply that increases the power available in response to power demand rather than consuming a high standby power.

PWR . Power.

Q Control . Response selectivity control. Varies the roll-off sharpness of a filter passband to control the selectivity of the band. Higher Q sharpens the response for greater frequency selectivity.

RCA Connector . An economical, coaxial cable plug/jack combination commonly used for audio and lower-frequency video signals. Couples signal and ground thru inner and outer conductors, respectively. Sometimes color coded by function such as signal (red/yellow/white) and ground (black).

RCA Inputs/Outputs . Signal connections presented with RCA connectors. These connectors are economical, plug-in coaxial types commonly used in audio and component video applications.

Regulated . Controlled or stabilized, as in a power supply output having reduced sensitivity to the varying load demands produced by signal variations. A regulation specification quantifies the residual sensitivity as the percentage output variation induced by a given load demand.

Short Circuit Protection . Internal protection that prevents damage during an output short or other current-demand overload. This protection may be of the instantaneous, electronic type or the delayed, thermal type.

Signal-to-Noise Ratio . SNR. The ratio of signal to noise in their composite signal, as generally expressed logarithmically by SNR(dB) = 20log (es/en) where es and en represent the signal and noise components of the composite, respectively. Higher signal-to-noise ratios indicate greater suppression of the noise signal's significance.

Silent turn-on/off . A feature that avoids speaker noise associated with turn on and turn off; typically by design limiting the rise and fall rates of power supply voltages during power cycling. This avoids the speaker pop sometimes produced by an amplifier's internal on/off bias transitions.

Slew Rate . The rate-of-change of a signal expressed in volts/second. Most notable in the slew rate limiting that reduces an amplifier's bandwidth at larger signal levels.

SMT . Surface Mount Technology. A high-density electronic component mounting alternative used for compactness and automated assembly economies. This alternative eliminates the wire interconnect leads and packages of conventional electronic components by soldering unpackaged components directly to a printed circuit board.

S/N Ratio. Signal-to-Noise Ratio. A noise performance measure of a signal or the electronic component that supplies it, reflecting the ratio of the signal amplitude to that of the accompanying noise.

SNR . Signal-to-noise ratio . ( See also S/N Ratio.)

Soft Start . Gradual enable of internal power supplies to avoid speaker "pop" during turn on. (See Silent Turn-on/off.) The resulting gradual rise in an amplifier's power supply voltages avoids the rapid transitions in internal biases that could produce an erroneous output signal spike.

Soft Turn-on . ( See Soft Start, Silent Turn-on/off.)

Spectrum Analyzer. An instrument that detects and displays signal amplitude versus frequency. Provides a visual display of audio-signal amplitude versus frequency to identify the relative contributions of bass, midrange and treble components and subdivisions of these components by frequency.

Stable. For an electronic circuit, remaining in a controlled state with no evidence of oscillation.

Stable, x ohm . Stable under a load condition as low as x ohms where x is the load (speaker) impedance. Lower impedance loads conduct higher current levels from an amplifier's output and those currents produce parasitic voltage drops on the amplifier's power supply lines and at the power supply output. Those parasitic drops can act as feedback signals to produce oscillation under low impedance loading conditions.

Surround Sound . That sound produced by an audio system having separate left, right and center audio channels and speakers. Basically stereo sound with the addition of a center channel that combines left and right signals.

Switching Power Supply . A power supply that employs internal on/off switching for high power efficiency. An economical and space saving alternative with the disadvantage that the supply's switching operation produces high-frequency electrical noise.

Terminal . A wire or cable connection point. May be a socket, screw-down connection, spring clip, etc.

Thermal Protected . Having temperature-sensing overload protection, such as sometimes used in amplifier output stages to protect against sustained high current demands. Thermal protection is superior to simple current limiting because the thermal alternative only activates when the high temperature consequence of an overload occurs. In contrast, current limiting activates immediately even though the potential for high temperature damage has not yet developed. Thus, a thermally protected circuit still accommodates some signal transients that would be unnecessarily blocked by simple current limiting.

Treble . The higher frequency range of the audio spectrum which requires mechanically precise audio speakers, called tweeters, for the reproduction of shorter sound wavelengths.

Tri Mode . A speaker connection flexibility of an amplifier output that permits grounded, floating or bridged speaker loads. Grounded speakers reproduce one channel of a stereo signal. Floating and bridged speakers are differentially driven by both signal channels for a center channel response.

V . Volt. The unit measure of electrical voltage.

VAC . Volts, AC.

VDC . Volts, DC.

Vp-p . Volts Peak-to-Peak. The excursion range of an AC voltage signal between its positive and negative extremes.

Vrms . Volts, root-mean-square. A time averaged measure of an AC voltage signal that more directly reflects the power delivery potential of the signal.

VU Meter . A meter providing a visual indicator of average signal level particularly useful in adjusting recording levels.

W (Watt). A unit measure of electrical power equaling the product of voltage and current.

X-Bass . Extra Bass. (See also XBS, Punch Bass.)

XBS . Extra-Bass-System. (See also XBS, Punch Bass.)

XLR . A three-pin, locking connector configuration commonly used in professional audio and sometimes in consumer audio to minimize coupled noise interference. The three pins accommodate the two stereo channels and ground.

Batteries

A . Ampere or amp. The unit measure of electrical current.

AH . Amp-Hour. A battery capacity rating that equals the achievable product of the current drain and the time duration of that drain. The greater the AH rating, the longer the operating battery life. For a known current drain requirement, dividing the amp-hour rating by that drain yields the operating time duration of the battery supply.

Battery Memory . A residual-charge characteristic of some battery types that prevents complete recharge until full discharge has occurred. Reduced operating time following charging may indicate this condition. To overcome the problem, some battery chargers offer the option to fully discharge such batteries prior to recharge.

Li-Ion . Lithium Ion; a long-life battery material combination.

Lithium Ion (Li-Ion). A long-life battery material composition.

mA . (Milliamp). 0.001 amp.

mAh . Milliamp-hour. The current-time rating of battery capacity which equals the product of the current drain and the time duration of the drain. Dividing the mAh rating of a battery by the current drain of a device it powers yields the sustainable time of the battery supply.

Memory Effect . A characteristic of some rechargeable batteries in which residual internal effects prevent full re-charge of the battery, particularly when the battery has not been fully discharged. For a battery powered device, reduced operating time between charges potentially indicates memory effect rather than battery degradation. In such cases, complete discharge may restore operating time.

Milliamp . One thousandth of an amp (.001A).

mV . (Millivolt). 0.001 volt.

NiCad . Nickel-Cadmium. A rechargeable battery material combination. Economical but subject to a memory effect that can eventually prevent full recharge.

NiMH . Nickel-Metal-Hydride. A rechargeable battery material combination having much greater capacity and none of the memory effect of NiCad equivalents.

VDC . Volts, DC.

Cameras

AE . Automatic Exposure. Electronic control over a camera's shutter speed or f stop to ensure accurate exposure level. This control prevents blurred or poorly exposed photos. Selecting a shutter priority exposure mode fixes shutter speed while varying the f stop to control exposure. This mode best serves action photos where a high shutter speed is required to freeze motion in the photo. Alternately, selecting an aperture priority exposure mode fixes the f stop while varying the shutter speed to control exposure. This second mode best serves photos where a greater depth of field is required to maintain focus throughout the foreground and background.

Aperture Priority (Camera). Automatic exposure control achieved with a fixed aperture and variable shutter speed. With a fixed aperture, the automatic control sets the shutter speed to whatever level required for proper exposure. This aperture/speed combination preserves image depth of field or range of focus but can sacrifice the motion stopping benefit of a shutter priority alternative.

Bitmap . A digital image storage format used by digital cameras and some video display drivers. This map stores the color and brightness information for each pixel of an image.

B/W . Black and White.

Camcorder . Camera/recorder; specifically, the video combination. A camera that records on video tape.

Halogen. An inert gas sometimes contained in strobe light enclosures .

Hot Shoe . A camera strobe mount incorporating a firing control connection. Provided for mounting an external strobe without the need for a separate wire connection from the strobe to the camera.

ISO. An international standard that defines film speed ratings.

kb (kilobyte). Thousand bytes where a byte is a unit of digital memory. For a digital camera, the number of kb of memory determines the number and resolution of the images that can be stored.

LUX . A unit measure of light intensity used in rating the output power of photographic strobes.

Self Timer . A camera feature that delays the shutter trip until a predetermined time after depressing the shutter release. Permits self portraits. Also permits longer term exposures that would be compromised by a hand held camera.

Shoe Mount . A strobe mounting connector included on many cameras. In addition to serving as a mechanical mount, the shoe generally makes electrical connections to the strobe to control its operation.

SLR Camera . Single-Lens-Reflex cameras couple the viewfinder image directly through the film imaging lens. This offers the advantage of automatic viewfinder adjustment to the specific lens attached to the camera. Thus, switching from a normal view lens to a telephoto, wide-angle or macro lens automatically compensates the viewed image to match that transmitted to the film. This direct coupling also assures the appropriate light transmission to internal exposure metering/control circuits.

Telephoto Lens (nX) . A telescopic lens having a magnification factor of n:1 and reducing the image field by the same factor. Primarily useful for distant objects and not generally suitable for close up applications. The converse of a wide-angle lens.

TTL . Through-The-Lens as in single-lens reflex cameras (SLRs). Provides a direct viewfinder image of the scene to be photographed with the lens currently attached. Changing lens also changes this image for automatic viewfinder adjustment. Frequently includes exposure monitoring and/or control using this same image.

VDC . Volts, DC.

Wide-Angle Lens (nX) . A lens that widens the image field-of-view through a n:1 image size reduction. The converse of a telephoto lens.

Zoom Lens . A camera lens having variable focal length for controllable magnification. Permits lens adjustment to control the camera's field of view without moving the camera itself. Simultaneously alters the apparent image depth with longer focal lengths compressing distance and shorter ones expanding it. The variable control generally spans focal lengths from wide-angle, through normal to telephoto.

CD Players

Bass Boost . Increased bass signal for greater low-frequency sound.

CD . Compact Disc; a digital audio disc.

CDR . Recordable CD, typically a record-once disc.

CD-RW . Re-Writable CD, capable of multiple re-recordings as opposed to the single recording capability of a CDR.

D/A converter . Digital-to-analog converter, as used to convert the digital signal of a CD to an analog audio signal. The precision and dynamic range of this conversion depends upon the number of bits resolved by the D/A converter. 16 bits represents the standard for high performance audio applications and provides a 96 dB dynamic range.

DAC . (See D/A converter.)

Digital . Signal representation thru a series of either 1 or 0 (on or off) states. Contrasts with analog representation where signal amplitudes exist at any level. In audio, the digital encoding of CD and DAT sources expands dynamic range and suppresses noise.

Digital-to-Analog Converter . (See D/A converter.)

DNR . Digital Noise Reduction. The application of digital signal processing (DSP) algorithms to reduce the effects of noise.

DSP . Digital Signal Processing. In audio, the application of digital signal-processing algorithms primarily to reduce the effects of noise (DNR) or to produce specialized audio effects.

Frequency Response . The range of signal frequencies supplied by an amplifier or reproduced by a speaker or microphone as specified by the upper and lower bounds of the frequency range in Hertz (Hz). Typically, 20Hz to 20kHz encompasses the full range of human hearing and separate audio speakers generally serve different segments of this range.

Hz . Hertz. A unit measure of signal frequency expressing signal cycles per second. Typically, 20Hz to 20,000Hz encompasses the full range of human hearing.

kHz kilohertz . A measure of signal frequency expressing thousands of cycles per second. (1 kHz = 1000 Hz).

MD . Minidisc. A 2.5" CD for compact/portable applications.

MiniDisc . A 2.5" CD for compact/portable applications.

Punch Bass . Bass boost. Increased low-frequency audio signal drive used for emphasized bass components and/or to compensate for restricted low-frequency speaker response. Especially effective with headphones as size restrictions then preclude the use of traditional low-frequency transducer elements.

RCA Inputs/Outputs . Signal connections presented with RCA connectors. These connectors are economical, plug-in coaxial types commonly used in audio and component video applications.

VAC . Volts, AC.

Vrms . Volts, root-mean-square. A time averaged measure of an AC voltage signal that more directly reflects the power delivery potential of the signal.

W. Watt. A unit measure of electrical power equaling the product of voltage and current.

X-Bass . Extra Bass. ( See also Punch Bass.)

XBS. Extra-Bass-System. ( See also Punch Bass.)

Headphones

Circumaural (Headphones). Ear surrounding; covering the ear. The circumaural configuration blocks ambient audio interference. In contrast, Open-Air headphones admit ambient sound.

Frequency Response . The range of signal frequencies supplied by an amplifier or reproduced by a speaker or microphone as specified by the upper and lower bounds of the frequency range in Hertz (Hz). Typically, 20Hz to 20kHz encompasses the full range of human hearing and higher quality headphones realize this full response.

Hz (Hertz). A measure of signal frequency expressing signal cycles per second.

Imaging . Acoustically portrayed location produced by a playback sound source, primarily through stereo effect but also through relative sound intensity. The stereo effect communicates left/right position and the sound intensity communicates relative distances.

Infrared . Light at frequencies below the red end of the visible spectrum. Often used for signal coupling in wireless headphones and in TV remote controls. Use of infrared light distinguishes the signal coupling light from normal room lighting. Infrared also provides a more economical control link than the RF alternative but it remains limited to line-of-sight coupling.

Mini Phone Connector . A 1/8" diameter plug-and-jack connector commonly used on headphone cables.

NC . Noise Cancellation. A feature added to some headphones that removes ambient noise interference through signal cancellation.

Open-Air . Open space design partially vents and receives acoustic energy to avoid the image restricting confinement of totally isolated stereo signals. However, in the process, the open-air design does emit sound to the surrounding environment.

Phone Connector . A ¼" diameter plug-and-jack connector commonly used for headphones.

RF. Radio-Frequency.

RFI . Radio Frequency Interference. Electrical noise at radio frequencies that produces reception interference. Sometimes produced by auto ignition systems, electric motors and lightning. The resistance ignition cables commonly used in cars greatly reduce this source of RFI.

VAC . Volts, AC.

VDC . Volts, DC.

Vrms . Volts, root-mean-square. A time averaged measure of an AC voltage signal that more directly reflects the power delivery potential of the signal.

W (Watt). A unit measure of electrical power equaling the product of voltage and current.

Receivers

Adj-Ch . Adjacent channel. A channel adjacent to a receiver's tuned channel and requiring rejection to prevent interference with the desired channel reception. Lack of this rejection results in two or more signals mixing together in the receiver's audio or video output.

AFC . Automatic Frequency Control. Automatic stabilization of a receiver's tuned frequency through use of an internal reference frequency source. Comparison of the signal received against the reference frequency permits automatic tuning adjustment for optimum tuning accuracy and correction of tuning drift with time.

AGC . Automatic-Gain-Control. Automatic stabilization of a receiver's output signal volume through comparison of that signal with an internal reference level. This prevents sound volume variation with time and/or location. Particularly useful in mobile applications like car radios where a varying location alters the received signal strength. AGC automatically compensates for such variation to maintain a set output level.

AM . Amplitude Modulation, as employed in AM radio broadcast. This modulation varies a carrier signal's amplitude or magnitude to encode it with the desired broadcast signal. The encoded signal is then broadcast at the station's designated carrier frequency. A radio receiver detecting that signal demodulates it or separates the desired modulation component from the carrier.

AMS . Automatic music sensor. A tape player feature that fast forwards to the starting point of the next music track by sensing the presence of the next recorded signal. At that point, fast forward stops and play resumes.

Attack Time . The time required to actuate a limiter following a signal crossing of the limit threshold. During this turn on time, unattenuated signal continues to pass through the circuit. However, the high speed of electronic switching generally makes this effect negligible for audio frequencies.

Automatic Volume Control . Automatic, electronic variation of gain to maintain constant output volume. This feature is most useful in auto radios where the changing signal conditions encountered in travel would otherwise result in a varying audio volume.

Band . A frequency range of operation, such as the AM and FM bands of commercial radio or the multiple operating bands of a CB transceiver.

BNC . A bayonet-style locking connector for coaxial cable connections commonly used for the higher frequency radio and video signals. Provides a highly-reliable low-loss connection consistent with the requirements of RF coupling.

BSM . Best-Stations-Memory station selector presets. A car radio feature that permits programmed assignment of specific radio tuning frequencies to selector buttons.

CB . Citizen Band. A two-way radio broadcast band assigned for unlicensed public use.

COAX . Coaxial; having a common center axis as with the two conductors of a coax cable or coax connector.

COAX Cable . A cable having two coaxial conductors with the outer conductor serving as an electrical noise shield for the inner one. In addition, the well controlled physical geometry of the cable defines its characteristic impedance, as required for efficient RF coupling through impedance matching. COAX is the best cable solution for coupling low-level antenna or dish signals to TV sets and VCRs. Requires the installation of COAX connectors at the ends of each cable run.

Coaxial . Having a common center axis as with the two conductors of a coax cable. The coaxial structure of such cable makes the outer conductor an electrical shield for the inner conductor and controls the cable's impedance.

Coil . An inductor; an electronic component whose impedance increases with increasing frequency. Useful in blocking the transmission of higher-frequency signals. Primarily used in RF applications.

Crosstalk . Parasitic coupling between signal channels. At audio frequencies, crosstalk normally results from ground loops introduced by the use of one ground return for more than one high-current signal path. In one example of crosstalk avoidance, separate ground return lines for the two speakers of a stereo system avoid such cross coupling.

Crystal-Controlled (Oscillator). Highly-stable frequency control achieved with a quartz crystal. Used in precision radio tuning where the frequency of a reference oscillator serves a standard.

EL . Electro-Luminescent. An illuminated display often found in auto radios that employs electro-luminescence rather than an incandescent bulb to light the display.

FM . Frequency Modulation; as in FM radio broadcast. Signal modulation of a carrier signal through variation of the carrier's frequency. This contrasts with the amplitude modulation of AM broadcast where the carrier's amplitude rather than frequency is varied. Noise interference more directly affects signal amplitude and, thereby, AM radio signals, giving rise to the demand for higher fidelity through FM broadcast. However, the higher carrier frequencies allocated to the FM band typically result in a shorter effective transmission ranges.

FRS . Family Radio Service.

Hz (Hertz). A measure of signal frequency expressing signal cycles per second. Typically, 20Hz to 20,000Hz encompasses the full range of human hearing.

Impedance . The electrical characteristic of an electronic device that fundamentally reflects the voltage developed in response to a current supplied to the device. For receivers, impedance matching between the antenna, the antenna cable and the receiver input assures optimum signal coupling.

Inductor . An electronic component whose impedance increases in proportion to signal frequency. Useful in blocking the transmission of higher-frequency signals such as in blocking high-frequency coupling from woofers. Also used in RF impedance matching networks.

Input Sensitivity . The minimum input signal level reliably detected by a device, such as that required by the input of a receiver. Generally, the internal noise level of the device sets this minimum signal requirement.

kHz. (kilohertz). A measure of signal frequency expressing thousands of cycles per second. (1 kHz = 1000 Hz). Audio signals extend up to 20kHz.

MHz . (Megahertz). A measure of signal frequency expressing millions of cycles per second. TV signals and many radio signals are commonly broadcast in the MHz range.

PLL . Phase-Locked Loop. A frequency-selective feedback loop used for electronic tuning within radio and TV receivers. Provides high-selectivity channel tuning with microelectronic compatible components. Bypasses the need for lossy, large inductor elements in tuning circuits.

Power . The amount of electrical energy supplied to or consumed by a device, such as supplied from an amplifier to a speaker or from the power line to the amplifier, as specified in Watts (W).

RCA Inputs/Outputs . Signal connections presented with RCA connectors. These connectors are economical, plug-in coaxial types commonly used in audio and component video applications.

RF . Radio-Frequency or, more generally, having to do with high frequency broadcast transmission and reception.

RMS . Root-Mean-Square . An amplitude measure of an electrical signal used to reflect the net power capability of a signal or a speaker. Note that this differs from the peak power, which reflects the maximum instantaneous power capability.

RX . Receive, as with a CB transceiver.

Seek Tuning . Automatic radio station select that seeks out the next signal having tunable strength. Activated by a front panel button for either forward or reverse channel seek.

Sensitivity . A measure of minimum acceptable signal level, such as that required by the input of a receiver. Sensitivity specifications define a receiver's minimum signal and, there, a low number reflects a high degree of receiver sensitivity.

Shielded Cable . A cable having an outer shield conductor that often also serves as the ground return. That outer conductor absorbs coupled interference signals to protect the inner conductor that carries the intended signal.

SMT . Surface Mount Technology. A high-density electronic component mounting alternative used for compactness and automated assembly economies. SMT frequently replaces printed circuit board assemblies that require thru-board holes for package leads by solder connecting leadless unpackaged components directly to a PC board.

Terminal . A wire or cable connection point. The termination point of a conductor segment. May be a socket, screw-down connection, spring clip, etc.

TX . Transmit, as with CB transceivers.

UHF . Ultra-High-Frequency. A broadcast frequency band.

VAC . Volts, AC.

Vrms . Volts, root-mean-square. A time averaged measure of an AC voltage signal that more directly reflects the power delivery potential of the signal. The most common measure of AC voltage magnitude.

VU Meter . A meter providing a visual indication of average signal level particularly useful in setting recording levels. Sometimes implemented with a vertical column display where the illuminated column height displays signal magnitude.

W (Watt). A unit measure of electrical power equaling the product of the voltage and current supplied by or consumed by a device.

Speakers

A . Ampere or amp. The unit measure of electrical current.

Acoustic Suspension . A speaker construction alternative in which a sealed enclosure traps air to serve as a spring-like return.

Baffle . The front mounting surface of a speaker enclosure. That surface also serves to suppress emission of the opposing-phase sound waves produced by the backs of speaker cones, making the baffle a significant enclosure element.

Basket, Speaker . A speaker's mechanical frame that suspends the speaker cone(s). Also serves as a basic mounting bracket but adapter brackets may be required for specialized installations such as encountered in cars.

Bass Reflex . A woofer enclosure having a tuned port for enhanced bass response. The tuned port is a tubular enclosure opening that is dimensionally tuned to enhance a narrow frequency range.

COAX Speakers . Two speakers serving different frequency ranges internally joined on a common axis for space and mounting efficiencies. Typical combinations include a tweeter and midrange speaker having a common center-mounted driver.

Cone . The conical diaphragm of a speaker. That portion of a speaker surrounding the central driver.

Continuous Power . In a speaker system, the maximum average-operating power permissible. A speaker can withstand greater momentary power excursions, like those of music peaks, but a greater power continuously would potentially produce damage.

Crest Factor . The ratio of peak instantaneous power to the average power. Most speakers can accept short term power peaks that significantly exceed the continuous power rating, as expressed by crest factor. No speaker damage will result as long as the average power remains within the speaker's rating.

Crossover . A transition frequency separating two regions of operation, such as the crossover frequency of a speaker system between bass and midrange or between midrange and treble. Crossover networks divide audio signals into these separate frequency ranges to permit individual response adjustments within the ranges and to separate the signals driving the corresponding speaker elements.

Crossover Frequency ( See Crossover).

Crossover Network . A multiple bandpass filter that separates an audio signal into frequency ranges such as bass, midrange and treble for separate signal control and for separate drive of woofer, midrange and tweeter speaker elements.

Crossover Slope . The response roll off rate before or after the crossover frequency, typically 18 dB/octave. This slope defines the response selectivity of the crossover in separating its output frequency bands. High selectivity is desirable for isolation of specific frequency bands to their corresponding speaker elements.

Crossover, 3-Way . A crossover network supplying three frequency-separated outputs (bass, midrange and treble) for separate signal control and drive of woofer, midrange and tweeter speaker elements.

Crossover Type . Crossover classification by the response roll off rate before or after the crossover frequency. This defines the response selectivity of the crossover in separating two frequency bands. Typically 18 dB/octave, indicating a three-pole response roll off. (See also Crossover Slope.)

Cutoff . The upper or lower limit of a frequency response. A response roll off frequency like those separating the bands of an equalizer or like the frequency limits of a speaker response.

Damping Factor . A measure of the ability of an electronic circuit to prevent the introduction of extraneous signal resonances. A damping factor of 1.0 or greater assures the suppression of such resonances. In audio applications, adequate damping is particularly important in speaker and speaker enclosure responses because mechanical resonances there would disturb response flatness.

Diaphragm . The cone or dome of a speaker that vibrates in response to signal drive, producing sound pressure waves. The fabric portion of a conical speaker or the dome itself in a dome speaker.

Directivity (Speaker). The sound radiation pattern or the way output sound waves spread from a speaker. In general, a wide horizontal spread and a narrow vertical spread best serve audience spatial configurations or a varying listener position within a room.

Dispersion . The sound radiation pattern or output spread of a speaker (Directivity) over a given angle. (See Also Directivity)

Dome Tweeter . A tweeter having a dome rather than cone shaped diaphragm for wider sound dispersion. Tweeter response with a conventional cone diaphragm lacks the spatial dispersion afforded lower frequency signals and a dome diaphragm compensates for this limitation at the tweeter's higher frequencies.

Downfiring Speaker . A speaker that projects its acoustic signal downward rather than outward. Sometimes preferred for woofers and subwoofers to achieve sound spreading through floor reflections. That spreading avoids the localized effect of conventional front firing speakers for greater surround effect.

DPL . Dolby Pro Logic; a surround sound system developed by Dolby Laboratories.

Driver . In a speaker, the voice coil that drives the internal speaker vibration. Basically an electromagnet, the driver produces vibration in the speaker cone in response to the electrical audio signal.

DTS . Digital Theater Surround. A surround sound implementation having greater bandwidth potential.

DVC . Dual voice coil. A type of audio speaker having separate voice coils for two frequency ranges. Separate coils permit optimizing each for the specific frequency segment it serves. In this way, one speaker fills the function of two others such as a tweeter and a midrange. However, this combination inherently introduces compromises not found with the two independent speaker alternative.

Dynamic Speaker . A speaker having a permanent magnet for damping voice coil motion and for returning the voice coil to its neutral position. The most common speaker type for woofer and midrange applications.

Electronic Crossover . A crossover network formed with active rather than passive filters for greater response shaping control. The gain introduced by the active elements provides impedance isolation between crossover sections, removing interdependencies that otherwise compromise individual section responses. (See also Crossover Network.)

ESR . Electrical Series Resistance. The parasitic resistance of a capacitor. Presence of that resistance makes the capacitor non-ideal and limits its ability to remove electrical transients and noise. ESR becomes most significant at higher frequencies as the falling capacitive impedance then makes the parasitic resistance a greater proportion of the capacitor's impedance.

Excursion . The physical distance traveled by the speaker's voice coil in producing its acoustic output. Greater excursions correspond to greater output volume, as incorporated in long-throw woofers.

Ferrofluid . A particle filled oil that heat sinks a speaker's voice coil to its magnet for cooling. Metallic oxide particles in the fluid enhance the thermal conduction of the heat sinking. That heat sinking economically extends the speakers power capacity.

Frequency Range . A span of frequencies between specified end points. A response band or bandwidth. Individual speaker elements like woofers, midranges and tweeters serve different frequency ranges within the overall audio frequency range. (See also Frequency Response.)

F&R . Front and Rear, as in car audio volume balance.

Full-Range Speaker . A single speaker, often incorporating multiple speaker elements, intended for the full audio range. Offers a more compact and economical solution but this combination speaker can not match the combined performance of a woofer, midrange and tweeter.

GND . Ground. The zero reference point from which a voltage or voltages are measured. In the most basic case, earth ground. In electronic systems, generally the chassis or case of the system.

Ground Loop. A crosstalk producing condition in which the ground line currents from one signal produce voltage drops that add to another signal path. Star connection returns of all grounds at a common point avoids such parasitic interference.

HDF . High Density Fiberboard. An economical wood composite alternative often used for speaker cabinets when combined with a veneer finish. The high density of the fiberboard inhibits case resonances well but HDF lacks the durability and beauty of a solid hardwood.

Horn . A high-frequency speaker. ( See also Tweeter)

Hz (Hertz). A measure of signal frequency expressing signal cycles per second. Typically, 20Hz to 20,000Hz encompasses the full range of human hearing.

IMPP . Injection Molded Polypropylene. A common form of rigid plastic.

Inductor . An electronic element whose impedance increases with frequency. Sometimes used to decouple woofers from high-frequency signals by placing the inductor in series with the speaker's signal line. In such applications, the inductor's parasitic resistance must be much less than the speaker impedance to avoid significant signal loss.

In-wall . Designed for installation within a wall, as with in-wall speakers. In-wall speakers offer great placement flexibility and unobtrusive space demands but can not match the fidelity achievable with enclosure mounted speakers. By design, those enclosures enhance a speaker's acoustic result while a wall installation will more likely degrade it.

Kapton . A high-temperature electrical insulator film sometimes used in woofer voice coils.

Kelvar . A high-strength, heat-resistant fabric sometimes used for speaker diaphragms in higher priced models.

kHz (kilohertz). A measure of signal frequency expressing thousands of cycles per second. (1 kHz = 1000 Hz). Audio signals extend up to 20kHz.

LCR . Left, Center, Right.

Low Pass Filter . A filter that passes only signals below its cutoff frequency. In audio, such filters sometimes remove midrange and treble components from woofer or subwoofer drive signals.

Low-Q . Having a broader frequency response and less susceptibility to electronic resonance. A desirable amplifier and speaker characteristic that avoids the potential for exaggerated responses from resonance and peaking.

LP crossover . A Low-Pass crossover frequency or filter network that separates bass components from the overall audio signal. One of the signal separation boundaries of a crossover network.

LPF . Low-pass filter.

Magnetic Gap . The space in a speaker's magnetic field where the voice coil is suspended. This gap must be large enough to accommodate the voice coil's displacement but small enough to retain high magnetic field strength across the gap.

Magnetic Oil . Ferrofluid. A particle filled oil that heat sinks a speaker's voice coil to its magnet for cooling. Metallic oxide particles in the fluid enhance the thermal conduction of the heat sinking.

Magnetic Shielding . Shielding against electromagnetic interference such as that produced by transformers and speaker magnets. To be effective, the shield must have a high magnetic permeability as well as a high electrical conductivity. Steel posses both of these qualities while aluminum, although an effective electrostatic shield, lacks the permeability required for magnetic shielding.

MDF . Medium-Density-Fiberboard. A denser version of particle board often used for speaker cabinets because of its combination of economy and resonance damping qualities.

Midrange. The intermediate frequency range of the audio spectrum between bass and treble. Also, a speaker designed to reproduce that range.

Natural Resonance . The natural frequency of vibration of an object as determined by the object's physical dimensions. Natural resonance occurs in an object when struck by an audio wave having a wavelength equal to an even fraction of one of the object's dimensions. Then, the object vibrates in synchronization with that wave producing extraneous harmonics. Damping these harmonic vibrations requires the use of rigid, heavier materials for speaker enclosures.

Neodymium . A magnetic alloy alternative to ferrite for speaker magnets. Neodymium's greater magnetic field density reduces size for compact speaker applications and headphones.

Overload Protection . Internal protection against damage from signal overload. Typically activated by sensing current level or temperature in output transistors.

Particle Board . Wood chips and glue pressed into board shape to provide an economical alternative to natural wood. Its uniformity and rigidity make it well suited for low resonance speaker cabinets. (See also MDF.)

Passive Radiator . An undriven, secondary woofer diaphragm used for improved low-frequency response.

Peak Power . In a speaker system, the maximum instantaneous operating power. A short term capability, this power level exceeds the continuous rating to accommodate signal transients.

PEI . Poly-Ether Imide. A resilient, synthetic speaker cone material.

Phantom Mode . A surround sound alternative that diverts the low-frequency center channel signals to the main speakers. Used in the absence of a dedicated center channel speaker.

Phase Delay . An undesirable time shift of audio signals most pronounced at higher frequencies. Readily produced by bandwidth limitations, this delay is the source of phase distortion which degrades audio clarity.

Phase Linearity . The absence of phase delay.

Phase Reverse . A speaker drive option that reverses signal phase to permit sound synchronization with another speaker. One switch position will produce in-phase sound waves from the two speakers that compliment each other. The other position will produce out-of-phase waves that acoustically subtract to degrade sound. Listening tests while switching will determine the correct setting for synchronization. (See also Polarity Switch).

Phono Plug . A low-cost coaxial cable plug commonly used on audio and other low-frequency cables. Also called an RCA plug.

Polarity Switch . A phase reverse switch included on some amplifiers to permit phase reversal in a speaker drive. Used to check for speaker phase synchronization. Synchronized speaker drive produces additive sound waves while unsynchronized waves tend to produce canceling effects. In the absence of a polarity switch, simply reversing the two wire connections at one speaker produces the same effect but the time required then makes synchronization more difficult.

Polymer . A synthetic chemical compound, like plastic.

Polypropylene . A strong, flexible plastic material often used for speaker diaphragms.

Power . The amount of electrical energy supplied to or consumed by a device, such as supplied from an amplifier to a speaker or from the power line to the amplifier, as specified in Watts (W).

Power Handling . Power capacity such as the input power rating of a speaker. Sometimes separate short term and long term specifications define this capacity with considerably higher short term ratings that accommodate music transients.

PPS . Polyphenylene Sulfide. A type of plastic used for electrical insulation.

PTC . Positive-Temperature-Coefficient, as in electronic overload protection devices. Signal current passing through the resistance of a PTC device produces power dissipation that causes temperature rise. In response, the PTC device's resistance increases to reduce the current flow to a safe level.

RCA Inputs/Outputs . Signal connections presented with RCA connectors. These connectors are economical, plug-in coaxial types commonly used in audio and component video applications.

Satellite Speaker . Smaller speakers typically placed to the side that reproduce mid and higher frequencies.

Sensitivity . A measure of Sound Pressure Level defining the speaker output at 1 meter when driven with a 1 Watt input signal.

Soft Dome . A dome speaker diaphragm made of a flexible material such as a soft synthetic fabric.

Sound Field . The perceived spatial quality of audio reproduction. (See also Imaging.)

Sound Pressure Level (SPL). An acoustic measure of speaker output level expressed in dB. For most applications this level should be somewhere below 95dB.

Spk. Speaker

Spkr. Speaker.

SPL . Sound Pressure Level. An acoustic measure of speaker output level expressed in dB. For most applications this level should be somewhere below 95dB.

Spring Clip . A wire connector that clamps a stripped wire end under the spring tension of a shaped metal strip. Permits quick wiring connections but less secure than a screw terminal.

Stereo Imaging . Acoustically portrayed location produced by a playback sound source, primarily through stereo effect but also through relative sound intensity. The stereo effect communicates left/right position and the sound intensity communicates relative distances.

Subwoofer . A speaker having a low-frequency response extending below that reproduced by a conventional woofer. With a response typically 200 Hz and below, its output remains nondirectional, making its location noncritical. Often mounted in a separate cabinet and may include a built-in amplifier for greater output.

Terminal . A wire or cable connection point. The termination point of a conductor segment. May be a socket, screw-down connection, spring clip, etc.

Three-Way (3 Way). Triple voice coil or a three-way combination speaker that serves woofer, mid-range and tweeter functions. Three-way speakers offer a compact alternative for space limited installations like car stereo. For other applications, separate woofer, mid-range and tweeter elements still offer the best quality and imaging alternatives.

Transient . An event of short duration like an instantaneous peak in an audio signal or a power line spike.

Treble . The higher frequency range of the audio spectrum which requires mechanically precise audio speakers, called tweeters, for the reproduction of shorter sound wavelengths. Treble frequencies add clarity and brightness to audio playback and their absence results in a somewhat muffled effect.

Tri Mode . A speaker connection flexibility that permits grounded, floating or bridged speaker loads to choose either a stereo or mono (center channel) response from each speaker. This option requires Tri Mode output provision on the audio source (amplifier, receiver, etc.).

Tuned Port . A tubular speaker port dimensionally tuned to enhance a narrow frequency range. Primarily used with woofers. The tuned port introduces a tunnel effect to channel sounds within its frequency range. Appears like an empty cylinder extending back from the mounting surface of multi-speaker enclosures.

Tweeter . A high-frequency or treble speaker that adds clarity and brightness to audio sound. Its high-frequency role allows a tweeter to be small for easy placement or installation. Found most often in speaker systems where it is recognized as the smallest of the three. Often a dome speaker.

Two-Way (2 Way) Speaker. Dual voice coil, DVC, or having two integral speakers, such as a mid-range and a tweeter, combined on a common speaker frame. This combination provides a more complete coverage of the audio sound spectrum than a single speaker element. Also, the two-way alternative does not require the separate mounting spaces of two independent speakers.

Variable Crossover . Having manual control over the crossover frequencies of a speaker system or the signals supplied to it. This variable feature provides a frequency-based audio balance between bass and midrange or between midrange and tweeter.

Voice Coil . The electro-mechanical driver of a speaker that translates electrical drive signals into mechanical motion in the speaker elements. The coil forms an electromagnet that attracts or repels the speaker's permanent magnet to drive the

W (Watt). A unit measure of electrical power equaling the product of the voltage and current supplied by or consumed by a device.

Woofer . A speaker serving the lower end of the audio range to reproduce bass sounds. In a three-speaker system, the woofer is recognized as the largest of the three, as physically required for its low frequencies. (See also Subwoofer.)

Tape Players

Auto Reverse . A tape player feature that reverses tape direction and channel at end of tape. This automatic reversal continues play with the other recorded channel, rather than stopping the player like the more common Auto Stop option.

Auto Stop . A tape player feature that stops tape drive at end of tape, rather than continuing play like an Auto Reverse option.

DAT . Digital Audio Tape. A digital storage format that extends much of the high dynamic-range and low-noise benefit of CDs to tape.

Dropout . Signal loss during tape playback often due to mechanical shock or vibration. Particularly important in portable tape players.

EP . Extended Play. A lower-speed tape recording mode that extends recording time. Frequently included in VCRs to accommodate longer recording requirements. However, the lower speed also reduces recording quality.

FF . Fast Forward. A rapid advance feature of tape players and recorders. Similar to Rewind but in a forward direction and generally slower to permit selective bypass of tape sections. Sometimes combined with AMS (Automatic Music Sensor) to permit fast forward advance to the next recorded track.

Hz. Hertz. A measure of signal frequency expressing signal cycles per second. Typically, 20Hz to 20,000Hz encompasses the full range of human hearing.

Impedance . The electrical characteristic of an electronic device that reflects the voltage developed in response to a current supplied to the device.

kHz. kilohertz. A measure of signal frequency expressing thousands of cycles per second. (1 kHz = 1000 Hz). Audio signals extend up to 20kHz.

mA . Milliamp. 0.001 amp. One thousandth of an amp.

Mini Phone Connector . A 1/8" diameter plug-and-jack connector commonly used for headphone connections.

mV . (Millivolt). 0.001 volt. One-thousandth of a volt.

NR . Noise Reduction.

Repeat . A tape player feature that repeats play of the selection just completed or the one currently in play. Rewinds to the first available track start and resumes play.

REW . Rewind.

Shuffle . A tape player feature that employs random selection from the available tracks for playback variety.

TPS . Tape Program Sensor. Senses the tape location of a recorded track in the Advance mode to initiate playback.

VAC . Volts, AC.

VDC . Volts, DC.

W (Watt). A unit measure of electrical power equaling the product of the voltage and current supplied by or consumed by a device.

Wow and Flutter . Playback distortion resulting from tape speed variation. Its occurrence may indicate the need to use a cleaner tape.

Video

A/V . Audio/Video.

CCD (Charge-Controlled-Device). A semiconductor element commonly used for electronic light detection or imaging. Converts the photon energy of light to electrical charge for electronic processing.

CCTV. Closed-Circuit TV.

COAX . Coaxial; having a common center axis as with the two conductors of a coax cable or coax connector.

COAX Cable . A cable having two coaxial conductors with the outer conductor serving as an electrical noise shield for the inner one. Presents a well-controlled characteristic impedance to preserve matching for optimum signal transfer. The best solution for coupling low-level antenna or dish signals to TV sets and VCRs. Requires the installation of COAX connectors at the ends of each cable run.

CRT . Cathode Ray Tube; the picture tube of a TV set or computer monitor.

DPI . (Dots-per-inch.) A measure of video image resolution. Electronic video signals are composed of a multitude of pixels or dots each having color and brightness attributes. The greater the density of dots or DPI, the smaller the dot size and the sharper the resulting image.

DSP . Digital Signal Processing. The application of digital signal-processing algorithms primarily to reduce the effects of noise but sometimes to produce special sound effects.

DSS . Digital Satellite System. A dish antenna and decoder combination that receives satellite-coupled TV transmission.

DV . Digital Video. DVD based video. ( See also DVD)

DVD . Digital Video Disc. A high-capacity video equivalent of a CD containing both video and audio recordings for video (TV) playback. Sometimes produced with dual-layer or double-sided discs.

F-type connector . An economical coaxial connector commonly used for TV antenna or cable connections. Similar in size and shape to a BNC connector but lacking the BNC's bayonet locking feature.

HDTV . High-Definition TV. A higher resolution television system with twice the resolution of standard TV.

Hi8. A video tape format.

Hz . Hertz. A measure of signal frequency expressing signal cycles per second. Typically, 20Hz to 20,000Hz encompasses the full range of human hearing.

IEEE 1394 . A high-speed digital data-transfer interface for applications such as streaming video. Often used with digital camcorders.

LFE . Low Frequency Effects. A subwoofer sound track included on 5.1 channel DVDs.

Mini Phone Connector . A 1/8" diameter plug-and-jack connector commonly used for headphone connections.

NTSC . National Television Standards Committee or the color TV standard governing the transmission signal format used in the USA and Japan.

OSD . On-Screen Display. Often used to display an operating menu for TV channel selection and audio system control.

PAL . Phase Alternation by Line. A European TV broadcast signal standard.

PIP . Picture-in-Picture. A small, secondary image screen displayed in one corner of a primary TV image. Selecting an alternate channel for the secondary image permits monitoring one channel while viewing another.

Pixel . An individual dot component of a dot-matrix video image. In color video, each of many thousands of pixels displays in red, green or blue to contribute to the localized screen color. Adjacent pixel colors visually mix to define the composite color perceived.

RCA Inputs/Outputs . Signal connections presented with RCA connectors. These connectors are economical, plug-in coaxial types commonly used in audio and component video applications.

RF . Radio-Frequency or, more generally, having to do with high frequency broadcast transmission and reception.

RGB . Red-Green-Blue; the primary colors used in television and monitor images. Each pixel or dot element of the screen produces one of these three colors when activated by the screen drive signal. Combinations of these primary colors produce the broad range of screen colors displayed.

SCART . A 21-pin European connector standard commonly used for auxiliary video interconnects. The Euroconnector.

SECAM . The French color TV system or its defining standards.

SVGA . Super Video Graphics Adapter. A high-resolution version of the VGA color monitor resolution standard.

SVGA Connector . A 15 pin connector used for coupling the RGB and sync components of SVGA signals.

S-VHS . Super VHS. S-Video (high-resolution) version of VHS that produces 400 lines of resolution and improved color.

S-Video. Super Video . A high-resolution video standard .

S-Video connector . A four-pin DIN connector used in coupling brightness and chroma signals from accessories to a TV set.

SWR . Standing Wave Ratio. Used as a measure of antenna reception efficiency.

TFT . Thin-Film-Transistor, as in active matrix displays.

VAC . Volts, AC.

VCR . Video cassette recorder.

VDC . Volts, DC.

VGA . Video Graphics Adapter. A color monitor resolution standard developed for personal computer applications. (See also SVGA)

VGA Connector . A 15 pin connector used for coupling the RGB and sync components of VGA signals.

VHS . Video Home System. The most prevalent video tape recording format.

W (Watt). A unit measure of electrical power equaling the product of the voltage and current supplied by or consumed by a device.