Motorola APX Series User Manual page 121

transmit. When the PTT is released, the unit returns to
receive operation.
Radio Frequency
RF-The portion of the electromagnetic spectrum between
audio sound and infrared light (approximately 10 kHz to 10
GHz).
Repeater
Remote transmit/receive facility that re-transmits received
signals in order to improve communications range and
coverage (conventional operation).
selective switch
Any digital P25 traffic having the correct Network Access
Code and the correct talkgroup.
Squelch
Muting of audio circuits when received signal levels fall
below a pre-determined value. With carrier squelch, all
channel activity that exceeds the preset squelch level can
be heard.
Synchronous Serial Interface (SSI)
DSP interface to peripherals that consists of a clock signal
line, a frame synchronization signal line, and a data line.
Standby
An operating condition whereby the radio's speaker is
muted but still continues to receive data.
Status Calls
Pre-defined text messages that allow the user to send a
conditional message without talking.
Tactical/non-revert
The user will talk on the channel that was selected before
the radio entered the emergency state.
TalkAround
Bypassing a repeater and talking directly to another unit for
local unit-to-unit communications.
Talkgroup
An organization or group of radio users who communicate
with each other using the same communications path.
English
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