Operating Manual

March 2008 5100 ES Models II/III Portable Radio Operating Manual 5-3
Conventional Mode Features
5.3 Busy Channel Lockout
The Busy Channel Lockout feature (also called Transmit Disable on Busy) automatically
disables the transmitter if the channel is busy when the PTT switch is pressed. When the
transmitter is disabled by this feature, “Busy” is displayed, a busy tone sounds, and the
transmitter is disabled.
The Busy Channel Lockout feature can be programmed to operate as follows. Each
conventional channel can be programmed differently.
“Off” - Busy channel lockout is disabled and the transmitter keys even if the channel is
busy.
“Noise” - If a carrier is detected on the channel, the transmitter is disabled when the
PTT switch is pressed.
“Tone (NAC)” - If an incorrect Call Guard (CTCSS/DCS) or NAC code (see Section
5.14) is detected, the transmitter is disabled when the PTT switch is pressed. An
incorrect code is any code other than the one programmed for the current channel.
“Status (P25 Conv Only)” – Radio will monitor the outgoing status symbols of the
repeater tx channel. The radio is allowed to transmit if the idle symbol is detected.
If Busy Channel Override is permitted by programming, it is possible to transmit even
when the transmitter is disabled by this feature. Release the PTT switch and then quickly
press it again (within one second).
5.4 Call Guard Squelch
Tone or digital Call Guard squelch (also called CTCSS/DCS signaling) can be
programmed on each conventional analog transmit and receive channel in any order
desired. The reverse burst and turn-off code are always transmitted and also detected on
channels programmed with Call Guard squelch.
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 attenuated by a filter. Call Guard squelch must be used in both the transmitting and
receiving radio to be functional.