Jim Newton wrote:
>I've added Dans info to the existing data at
>http://techref.massmind.org/pots
>aka
>http://techref.massmind.org/techref/default.asp?url=pots
>

I found that info a couple of years ago scattered between half
a dozen articles in various magazines, and don't know of any
definitive source, and never had an opportunity to double check
it all. Maybe someone does have a definitive source. Ma bell?

- danM
==================


>-----Original Message-----
>From: pic microcontroller discussion list
>[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Dan Michaels
>Sent: Friday, August 18, 2000 18:55
>To: PICLIST@MITVMA.MIT.EDU
>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
>===================
>
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