Motorola EX500 Basic Service Manual page 86

G-2
Term
PL Private-Line® tone squelch: a continuous sub-audible tone that is transmitted along
with the carrier.
PLL Phase-Locked Loop: a circuit in which an oscillator is kept in phase with a reference,
usually after passing through a frequency divider.
PTT Push-To-Talk: the switch located on the left side of the radio which, when pressed,
causes the radio to transmit.
RAM Random Access Memory: the radio's RAM is loaded with a copy of the EEPROM
data.
Registers Short-term data-storage circuits within the Microcontroller.
Repeater Remote transmit/receive facility that retransmits received signals to improve
communications coverage.
RESET Reset line: an input to the Microcontroller that restarts execution.
RF PA Radio Frequency Power Amplifier
RIB Radio Interface Box
ROM Read Only Memory
RSSI Received Signal-Strength Indicator: a DC voltage proportional to the received RF
signal strength.
RPT/TA Repeater/Talk-Around
Softpot Software Potentiometer: a computer-adjustable electronic attenuator
Software Computer programs, procedures, rules, documentation, and data pertaining to the
operation of a system.
SPI (clock and data Serial Peripheral Interface: how the Microcontroller communicates to modules and
lines) ICs through the CLOCK and DATA lines.
Squelch Muting of audio circuits when received signal levels fall below a pre-determined
value.
Standby Mode An operating mode in which the radio is muted but continues to receive data
System Central Main control unit of the trunked dispatch system; handles ISW and OSW messages
Controller to and from subscriber units (see ISW and OSW).
System Select The act of selecting the desired operating system with the system-select switch.
(Also, the name given to this switch.)
TOT Time-Out Timer: a timer that limits the length of a transmission.
TPL Tone Private-Line
µC Microcontroller
UHF Ultra High Frequency
µP Microprocessor
VCO Voltage-Controlled Oscillator: an oscillator whereby the frequency of oscillation can
be varied by changing a control voltage.
VCOBIC Voltage-Controlled Oscillator Buffer Integrated Circuit
VHF Very High Frequency
VSWR Voltage Standing Wave Ratio
Definition