Most DTMF decoder chips have an output that transitions when a valid tone pair
is decoded. This output can be used to mute the transmit audio while the DTMF
tones are present, snf most repeater controllers have the option of muting the
DTMF control codes.
In the case of a single tone, the DTMF decoder will not work. But one of the
DSP audio processors will work to get rid of a single tone when it is in the
'notch' mode. I have an older Radio Shack DSP that renders CW uncopyable as
only a very short click at the beginning of each element is heard.
73 - Jim W5ZIT
--- On Fri, 10/24/08, cruizzer77 <[EMAIL PROTECTED]> wrote:
From: cruizzer77 <[EMAIL PROTECTED]>
Subject: [Repeater-Builder] DTMF/toneburst silencer/blocker
To: Repeater-Builder@yahoogroups.com
Date: Friday, October 24, 2008, 4:00 AM
Hi
I'm looking for a circuit which removes dtmf tones and maybe other
tonebursts from the rx audio before it is fed to the tx.
There are circuits around which use the MN3008 and MN3101 ics which
are both obsolete now so are no choice. One possibility would be to
replace them with similar ics from Coolaudio, but most likely these
would still be hard to get even though they're still made.
Does anybody have a different approach for such a tone blocker?
Thanks Martin
.
