[BC] dtmf tone filter solutions

[Mike McCarthy]

Full quote...

We used the same box for trapping automated ISDN feeds into our 
logger/content ingestion box. I can say it worked nearly flawlessly using 
ISDN. We've not yet tested it for use on a Tie-line or Comrex POTS codecs 
or VoIP.  That's a test we're gearing up to do...

Setting levels can be tricky at first.  But once the sending levels are 
placed in the sweet spot of the box and verified low distortion, it works 
very well at muting all forms of the DTMF.

I concur with Gary's observation that cell phones can and do corrupt DTMF 
tones.  Depending on the phone and carrier, I have heard some systems 
create the DTMF at the cell phone base station using codes sent by the 
phone for that very reason.  YMMV...

MM

At 06:52 AM 9/18/2008 -0600, Gary Peterson wrote
>I'm using a CircuitWerkes unit for unattended play-by-play on one of our
>AMs.  There is a slight delay through the box, that prevents hearing the
>leading edge of the DTMF tones.  I feed mix-minus back to the play-by-play
>guy, so the delay doesn't bother him.
>
>I did have to set the box to require longer DTMF tones, to prevent falsing
>when the announcer gets excited and starts shouting into the headset mic.
>It works very well from a land line connection.  However, it is very
>unreliable on a cellular call.  And, yes, the cell phone is configured for
>"long tones."  Apparently, the cellular network corrupts DTMF tones
>significantly.  I can instantly tell if the audio is originating from a cell
>phone, as it sounds "gurgley" to me.  If the play-by-play originates from a
>cell phone, we have to have a live board op.
>
>Gary, KØCX
>CE KFXS, KOUT, KKMK, KRCS, KKLS & KBHB
>
>" Anyone on this list used the circuitwerkes dtmf tone filter?
>I need to filter dtmf tones out of ballgame broadcasts, but I'm concerned
>the 'delay' latency may stress out the air talent. Or is it that noticable?
>Henry G. Royse, II "