Motorola APX 2000, Detailed Service Manual

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Glossary-6 Glossary
phase-locked loop A circuit in which an oscillator is kept in phase with a reference, usually
after passing through a frequency divider.
PL See private-line tone squelch.
PLL See phase-locked loop.
Power Control IC The power control IC is intended for closed-loop bias control of power
amplifiers. The device facilitates accurate control of the current
delivered to the power amplifier (PA) via a control voltage.
private-line tone
squelch A continuous sub-audible tone that is transmitted along with the carrier.
See also DPL.
Programmable
Read-Only Memory A memory chip on which data can be written only once. Once data has
been written onto a PROM, it remains there forever.
PROM See Programmable Read-Only Memory.
PTT See Push-to-Talk.
Push-to-Talk The switch or button usually located on the left side of the radio which,
when pressed, causes the radio to transmit. When the PTT is released,
the unit returns to receive operation.
radio frequency The portion of the electromagnetic spectrum between audio sound and
infrared light (approximately 10 kHz to 10 GHz).
radio frequency
power amplifier Amplifier having one or more active devices to amplify radio signals.
RAM See random access memory.
random access
memory A type of computer memory that can be accessed randomly; that is, any
byte of memory can be accessed without touching the preceding bytes.
read-only memory A type of computer memory on which data has been prerecorded. Once
data has been written onto a ROM chip, it cannot be removed and can
only be read.
real-time clock A module that keeps track of elapsed time even when a computer is
turned off.
receiver Electronic device that amplifies RF signals. A receiver separates the
audio signal from the RF carrier, amplifies it, and converts it back to the
original sound waves.
registers Short-term data-storage circuits within the microcontroller unit or
programmable logic IC.
repeater Remote transmit/receive facility that re-transmits received signals in
order to improve communications range and coverage (conventional
operation).
Term Definition