Service manual

OPERATION
3-28
April 2001
Part No. 001-9800-203
3.9.4 TALK-AROUND
Normally, all transmissions go through a repeater.
However, there may be times when a user is out of
range of the repeater system and unable to talk to
anyone even though the mobile being called may be
only a short distance away. In this situation, the
repeater talk-around feature can be used to transmit on
the receive frequency so that the transmission does not
have to go through a repeater.
Any conventional group can be programmed for
talk-around (if talk-around is enabled at the system
level). Talk-around is then enabled by simply selecting
one of those groups. There is no talk-around indicator
when it is automatically selected in this manner unless
it is indicated by the group alpha tag (high tier only).
With high tier models, talk-around can also be
selected by the TA option switch if the selected group
is programmed “Talk-Around = No”. When talk-
around is enabled by this switch, “TA ON” is flashed
in the display, and when it is disabled, “TA OFF” is
flashed. If the selected group is programmed Talk-
Around = Yes, talk-around cannot be turned off by the
switch. This would be indicated if neither “TA ON” or
“TA OFF” is flashed when the switch is pressed.
When another system or group is selected, trans-
ceiver power is cycled, or scanning is enabled, talk-
around always reverts to the default condition
programmed for the group. If talk-around is disabled
at the system level, it cannot be selected by the TA
switch (“NO TALK” is flashed if it is pressed) and it
cannot be programmed on any of the groups in that
system.
3.9.5 CALL GUARD SQUELCH
Introduction
Tone, digital, or inverted digital Call Guard
squelch can be programmed on each transmit and
receive channel in any order desired. There is also an
option to disable the reverse burst or turn-off code on
transmit channels programmed with Call Guard
squelch. The reverse burst and turn-off code are
always detected on receive channels programmed with
Call Guard squelch (if it is sent).
The Call Guard squelch feature eliminates
distracting messages intended for others using the
channel. This is done by using a subaudible tone or
digital code to control the squelch. This tone or code is
unique to a user or a group on that channel. This tone
or code is transmitted with the voice signal but is not
heard because it is in the subaudible range and is atten-
uated by a filter. Call Guard squelch must be used in
both the transmitting and receiving transceiver to be
functional.
CG Option Switch (High Tier Models)
With high tier models only, a CG option switch
can be programmed. This switch disables both receive
and transmit Call Guard squelch on the selected
system/group (the monitor mode disables only receive
squelch control). It does not affect squelch control on
other system/groups, or the operation of external
decoders. When Call Guard squelch is disabled by this
switch, “CG OFF” is momentarily displayed.
Conversely, when it is enabled, “CG ON” is displayed.
The CG On mode is automatically re-enabled when
the selected system/group is changed or transceiver
power is cycled.
Tone Call Guard Squelch
Tone-type Call Guard squelch utilizes subaudible
CTCSS tones from 67-254.1 Hz. Although there are
42 tones assigned, those above 33 are normally not
used because of their close proximity to the voice band
which starts at 300 Hz. In addition, tones 11, 39, 40,
41, and 42 are normally not used because they may
cause interference with adjacent tones (see Table 4-5).
A reverse burst can be transmitted when the push-to-
talk switch is released to eliminate the squelch tail
(noise burst) in the receiving transceiver. However,
both the transmitting and receiving transceiver must be
equipped with this feature for it to be utilized. The
reverse burst is a 180-degree phase reversal for a
period of time determined by the tone frequency.
Digital Call Guard Squelch
Digital Call Guard squelch (CDCSS) uses digital
data instead of subaudible tones to control the squelch.
This data consists of continuous repetitions of 23-bit
words. No bit or word synchronization information is