Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ames!sun-barr!lll-winken!attdso!westmark!dave From: dave@westmark.UU.NET (Dave Levenson) Newsgroups: comp.dcom.modems Subject: Re: caller ID Message-ID: <786@westmark.UU.NET> Date: 18 Mar 90 02:51:22 GMT References: Organization: Westmark, Inc., Warren, NJ, USA Lines: 19 In article , TERRY@SPCVXA.BITNET ("Terry Kennedy, Operations Mgr") writes: (in reply to Dan Warburton ) > The caller ID signal is a series of simple coded pulses _before_ each > ring cycle. The reason two rings are "required" for detection is to make > sure it got the complete information (and it matched). Almost correct. In NJ, and probably elsewhere, the caller-id information is sent as a string of ASCII characters at 1200 bps, on an audio-frequency carrier, using FM (actually, FSK) modulation (similar to, but not compatible with, the old 202 half-duplex modems). This data-burst is send once per call, after the first ring. There is no redundancy (other than a parity bit per character) and no guarantee of error-free delivery. -- Dave Levenson Voice: 201 647 0900 Fax: 201 647 6857 Westmark, Inc. Internet: dave@westmark.uu.net Warren, NJ, USA UUCP: {uunet | rutgers | att}!westmark!dave [The Man in the Mooney] AT&T Mail: !westmark!dave