Thanks guys,

Bob just defined my problem. The task is to recognize a busy signal from any
PBX. It's rather about recognizing a signal with some stable frequency. I
don't believe someone would be able to whistle into a mike a busy signal
accurate enough :-).

Igor Pokorny

> -----Original Message-----
> From: Bob Ammerman [mailto:RAMMERMAN@PRODIGY.NET]
> Sent: Saturday, August 19, 2000 2:31 PM
> Subject: Re: [PIC]: Modulated pulses
>
>
> All of the below is nominally correct. Unfortunately you will
> find quite a
> bit of variation in the real world, especially on PBX and key
> systems used
> in businesses.
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
> ----- Original Message -----
> From: Dan Michaels <oricom@LYNX.SNI.NET>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Friday, August 18, 2000 9:55 PM
> Subject: Re: [PIC]: Modulated pulses
>
>
> > Igor Pokorny wrote:
> > >Hello all:
> > >
> > >I would like to get any help how to find a busy signal on
> telephone line
> by
> > >a PIC knowing exactly neither the modulation frequency nor
> the length of
> > >pulses.
> > >Could someone tell me where to look for a theory or some example?
> > >
> >
> >
> > I think most of the following are correct:
> >
> > US TP SYSTEM
> > ============
> > D.C. Line Voltage (Talk Battery) - 48v with receiver
> on-hook, red wire
> > (ring) negative, 5v for off-hook (with 50-1000 ohm d.c.
> load on line).
> >
> > Ring Signal - 20-90 vp-p, at 20-40 hz.
> >
> > Dialtone - dual 345 and 440 hz sinewaves.
> >
> > DTMF Tones - 1 high-band plus 1 low-band sinewave at
> frequencies shown in
> > DTMF Table, at max transmission level of 0 dBm averaged
> over 3 sec (approx
> > 24.5v RMS), for minimum of 50 msec duration and 45 msec
> interdigit time.
> >
> > Busy Signal - dual 480 and 620 hz sinewaves, 0.5 sec on,
> 0.5 sec off.
> >
> > Ringback Signal (simulates phone being rung up) - dual 440
> and 480 hz
> > sinewaves, 2 sec on, 4 sec off.
> >
> > Receiver Off-Hook Tone (when someone forgets to hang up the
> phone) - quad
> > 1400, 2060, 2450, and 2600 hz tones, pulsed at a 5 hz rate.
> >
> > Speech Signals - 200 - 3400 hz, bandlimited.
> > ======================
> >
> >
> > I also have an appnote that shows a number of these signals on
> > a scope display:
> >
> > AN-PTB04 - Telephone System Testing Using the PTB
> >
> > http://www.sni.net/~oricom/appnotes.htm
> >
> > best regards,
> > - Dan Michaels
> > Oricom Technologies
> > ===================
> >
> > --
> > http://www.piclist.com hint: PICList Posts must start with
> ONE topic:
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>

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