TELECOM Digest OnLine - Sorted: Re: Touch Tone Blocking

Re: Touch Tone Blocking

Robert Bonomi (
Sun, 10 Apr 2005 19:31:59 -0000

In article <>,
Takoma Park Volunteer Fire Department <> wrote:

> I need to devise a way to keep users from playing touch tones over the
> paging system. If you can suggest a way to prevent users from
> sounding touch tones over the paging amplifier circuit post it here or
> E-mail direct. Be advised that my ISP's anti Spam software will
> generate a service message to which you will have to respond in order
> for me to receive your e-mail.

Please be advised that having been *spammed* too many times by said
ISP's 'anti-spam' software, because my address was *forged* as the
sender of messages being 'challenged', *ALL* such 'challenges' are
blocked at time of transmission.

You ask for a favor, and then expect people to jump through hoops to
tell you about it. "Sorry, Charlie", that dog doesn't hunt.

As for your 'problem', the real solution is "training". It is a
'personnel' problem, not a 'technical' one.

Technology cannot _prevent_ the problem, although it can "ameliorate"
it. a DTMF decoder chip, wired to interrupt the PA leads when tones
are detected is about as close as you can come. Put the decoder
_in_front_ of a 50-100ms 'delay line', and you can cut the PA off
_before_ the tones propagate through the delay line.

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