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

---
James Newton mailto:jamesnewton@geocities.com 1-619-652-0593
http://techref.massmind.org
All the engineering secrets worth knowing

-----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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