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RLC-4 V1.79 Copyright © 1998 Link Communications Inc. 9/18/98
repeater, whether those tones are entered from the repeater or from one of the connected links,
remotes, or even the autopatch. DTMF tones that are heard by the repeater receiver will be muted
before they go out the repeater, but they can still go out any connected links or remotes.
Sometimes you want this, so you can send tones down the links to control other sites. Other times,
you don't want tones to go down the links; in those cases you should turn on the DTMF mute for
the link port transmitters just like you did for your repeater transmitter (with command 007).
DTMF Mute Bypass:
The DTMF mute bypass can be used for sending DTMF paging codes over a repeater that normally
mutes DTMF tones or for passing commands out a link transmitter that normally mutes DTMF
tones. If enabled, it allows you press 'D' (or whatever your force-execution digit is - see command
078) as the first digit after keying up to disable the muting function until you unkey. When the 'D'
is detected, the controller will ignore any digits detected from that receiver until you unkey. It will
not mute those digits on any transmitter and it will not try to decode those digits and execute any
commands. The 'D' itself will be muted as soon as it is detected. If you do not have an audio delay
module, the first part of that 'D' will be heard and might mess up whatever you are passing tones to.
If the tones are going to another controller of the same kind, turn off the DTMF bypass on the
other controller so the 'D' won't cause it to ignore the digits. If the first part of the 'D' not being
muted is still a problem, you will have to get an audio delay for that receiver, turn DTMF mute off
and enter the digits without using a 'D' first, or use the controller's command to generate DTMF
digits (command 033).
Voice Falsing
As mentioned earlier, a DTMF decoder works by watching for 8 tone frequencies, 4 that represent
the row and 4 that represent the column of a 16 key DTMF keypad. If a row frequency and a
column frequency are detected at the same time, the decoder registers it as a valid digit.
Sometimes peoples' voices have those frequencies in them and cause the DTMF decoder to think
that a digit is present when it is not. If you have the DTMF mute turned on, this will cause it to be
activated and your voice will "drop out" for a couple of seconds as the controller thinks it is muting
a DTMF digit. If you have the cover tone turned on, you will hear it as well. The voice falsing of
the DTMF decoder is not the decoder's fault - it is just watching for those tones. There are a
couple of things you can do to reduce falsing. The first thing is to check all of your audio levels. If
you have the receive audio turned up too high at any point before it gets to the decoder, it may be
distorted, which adds harmonics and makes falsing more likely. You can make any remaining
falsing less annoying by setting the DTMF mute timer to be relatively short (1..2 seconds, or even
less if you have an audio delay module). If all else fails, it is possible to change a resistor value on
the controller to make the decoder less sensitive to voice falsing.
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