Motorola ASTRO Digital Saber, Service Manual, Page: 18 / 128

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Repeater Remote transmit/receive facility that re-transmits received signals in order to improve
communications coverage.
RESET Reset line; an input to the microcontroller that restarts execution.
RF PA Radio Frequency Power Amplifier
RSS Radio Service Software
RPT/TA RePeaTer/Talk-Around
RX DATA Recovered digital data line.
Signal Qualifier
Mode An operating mode whereby the radio is muted but still continues to analyze receive data
to determine RX signal type.
SCI IN Serial Communication Interface INput line
SLIC Support-Logic IC; a custom gate array used to provide I/O and memory expansion for the
microcontroller.
Softpot Software potentiometer; a computer-adjustable electronic attenuator.
Software Computer programs, procedures, rules, documentation, and data pertaining to the
operation of a system.
SPI Serial Peripheral Interface; how the microcontroller communicates to modules and ICs
through the CLOCK and DATA lines.
Squelch Muting of audio circuits when received signal levels fall below a pre-determined value.
SRAM Static-RAM chip used for volatile, program/data memory.
SSI Synchronous Serial Interface on the DSP56001 consisting of six signals and used for an RX
and TX modulated data interface to the ADSIC.
Standby Mode An operating mode whereby the radio is muted but still continues to monitor data.
System Central
Controllers Main control unit of the trunked dispatch system; handles ISW and OSW messages 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.
TSOP Thin Small-Outline Package
UART Universal Asynchronous Receiver Transmitter.
µC Microcontrol unit (see MCU).
VCO Voltage-Controlled Oscillator; an oscillator whereby the frequency of oscillation can be
varied by changing a control voltage.
VCOB IC Voltage-Controlled Oscillator Buffer IC
Vocoder VOice enCODER; the DSP-based system for digitally processing the analog signals,
includes the capabilities of performing voice compression algorithms or voice encoding.
VOCON VOcoder/CONtroller board
VSELP Vector Sum Excited Linear Predictive coding; a voice encoding technique used in ASTRO
digital voice.
VSWR Voltage Standing Wave Ratio