GLOSSARY
A
Acoustics
Acoustical
Active Devices
AF
AGC
All Call
Alpha
AM
Ambient
Ambience
Ampere
Amplitude
Amplifier
Analog vs.
Digital
The science of sound.
A term used to differentiate a sound signal from its electrical signal counterpart or representation. For example: A microphone converts an acoustical signal (from music or speech) to an electrical signal. A loudspeaker converts an electrical signal to an acoustical signal.
Devices requiring operating power (battery or other) in addition to the signal. Examples are transistors, integrated circuits, amplifiers, and intercoms.
Audio Frequency. Within the range of 20 hertz to 20,000 hertz. Automatic Gain Control.
For talk key assignment only. Activating an All Call key will also activate all talk keys to the left of the All Call key (up to, but not including another All Call key).
Alphas are the
Amplitude Modulation.
Conditions existing at a location. Example: ambient temperature. Background noise or sounds.
The amount of electrical current when one volt is applied to one ohm. Also equal to one coulomb of electrical charge passing a point in one second.
The size of analog electrical signal as opposed to its frequency or other parameters. Magnitude also indicates a size. Amplitudes focus more from the measurement viewpoint, for example: a one volt peak sine wave amplitude, a one volt average amplitude.
Usually an electronic device that increases the amplitude of an electrical signal. Examples include a microphone preamplifier that brings millivolt signals to volt levels. A power amplifier that makes a one milliwatt signal into a 10, 100, 1000, or more watt signal.
Analog (as opposed to digital) here refers to the way information is put onto an electrical signal. An analog signal varies in voltage or current in step with the signal it represents. In the case of the acoustic pressure wave from speech, the pressure wave is converted to an electrical signal by a microphone. The voltage from the microphone varies as the sound pressure from the acoustic wave. A digital electrical signal either represents a binary number 0 or binary number 1. Combinations of numbers represent the amplitude of the pressure wave. The pressure wave is sampled at a rate two or more times the highest frequency to be transmitted. Therefore, there are a sequence of digital numbers representing the speech over a period of time. The advantage of analog circuitry is that it is conceptually simple and relatively easy to create. The disadvantage of analog circuitry is that it is sensitive to distortion and the quality of the circuit design and
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