Abell A720T, Service Manual

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A720T (VHF) Service Manual V1.0
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6.2.6 CTCSS

Program receive(Rx) and transmit(TX) CTCSS code at channel setting.

You radio(Rx CTCSS pre-programmed) can only receive the signal which carries the same CTCSS code, can
receive any signal(no CTCSS code programmed) with the same TX and Rx frequency.

After TX CTCSS code pre-programmed, your radio will transmit pre-programmed CTCSS code with your
signal.
6.2.7 CDCSS

Programm receive(Rx) and transmit(Tx) CDCSS code at channel setting.

You radio(Rx CDCSS pre-programmed) can only receive the signal which carries the same CDCSS code, can
receive any signal(no CDCSS code programmed) with the same TX and Rx frequency.

After TX CDCSS code pre-programmed, your radio will transmit pre-programmed CDCSS code with your
signal
.
Tail Tone Elimination: To avoid tail tone for receiver after carrier disappear in the channel. Carrie will
disappear after speaker finish speaking, so the noisy tail tone will born when receiver radio cannot detect carrier.
When transmitting of signal with CTCSS/CDCSS finished, the signal will send a prompt tone to receiver radio,
so receiver radio can open squelch before carrier disappear to avoid noisy tail tone.