[BC] dtmf tone filter solutions

[RichardBJohnson at comcast.net]

Please excuse, but how did they get there in the first place?
You need to find the source of this interference and eliminate
it at its source.

DTMF is in-band signaling, right in the middle of the audio-
frequency spectrum. These tones are typically generated
at +8 dBm, the maximum level allowed on a phone line,
and the frequencies are subject to a 5% specification
drift over temperature. Any attempt to filter them out
will result in a severe loss of significant information
right in the middle of the audible frequency range.

Circuitwerkes made a  "Silencer II" which is no longer
available for just this reason. If you thought you could
signal something to happen in the studio by pressing
a telephone keypad button without anybody knowing
about it, you need to rethink your idea. You use sub-
audible tones for that, not DTMF!

--
Cheers,
Richard B. Johnson
Read about my book
http://www.LymanSchool.org


 -------------- Original message ----------------------
From: <wclu at glasgow-ky.com>
> Anyone on this list used the circuitwerkes dtmf tone filter?