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the monitor mode, take the microphone off-hook. The
monitor mode is indicated by
A conventional system must be selected to enable
monitoring. If the microphone is taken off-hook with
an LTR-Net/LTR system selected, scanning halts but
monitoring is not selected.
Per Group Monitor Enable/Disable
Each conventional group can be programmed so
that off-hook monitoring is disabled. It is then always
disabled on that group regardless of the current micro-
phone hanger state. Monitoring then must be
performed by the Transmit Disable On Busy feature
described in the next section. Scanning is still
controlled in the normal manner by the hook switch
state.
If monitoring is not disabled on a group, it is
enabled by taking the microphone off-hook. If off-hook
detection is disabled on a radio-wide basis as described
in Section 2.4.6, monitoring must be performed by the
following Transmit Disable On Busy feature.
2.11.2 TRANSMIT DISABLE ON BUSY
The Transmit Disable On Busy feature automati-
cally disables the transmitter if the channel is busy
(carrier present) and it has not been monitored before
the PTT switch is pressed. This feature is enabled or
disabled on each conventional group by programming.
When the transmitter is disabled by this feature,
the busy tone sounds briefly and "DSBL BSY" is indi-
cated on the lower line of the display. The receiver is
then enabled while the PTT switch is pressed so that
the activity on the channel can be monitored. It is not
possible to access a channel by holding down the PTT
switch (it must be released to make another attempt).
If this feature is not used or if the channel is being
monitored by an off-hook condition as described in the
preceding section, the transmitter keys even if the
channel is busy. In addition, the transmitter can always
be keyed by releasing the PTT switch and then press-
ing it again within 1 second.
Some repeaters may have delayed drop-out (hang
time) which causes this feature to disable the transmit-
ter even though no busy condition exists. If this is a
in the display.
2-25
problem, there is the option with this feature to allow
transmitting if the correct receive Call Guard tone or
code is detected.
2.11.3 RECEIVE-ONLY GROUPS
Conventional groups can be programmed so that
transmitting is disabled (monitoring only is allowed).
This is done by programming the Tx Option parameter
for "Disabled". If the PTT switch is pressed with one
of these groups selected, the intercept tone sounds and
"TX DSBL" is displayed.
2.11.4 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. It is then enabled by simply selecting one
of those groups. It is not selectable by an option
switch. There is no talk-around indicator unless it is
indicated by the group alpha tag.
2.11.5 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
OPERATION
April 1999
Part No. 001-9800-600
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