Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!netsys!vector!telecom-gateway From: westmark!dave@rutgers.edu (Dave Levenson) Newsgroups: comp.dcom.telecom Subject: Re: Caller ID Message-ID: Date: 11 Apr 89 20:41:47 GMT Sender: news@vector.Dallas.TX.US Organization: Westmark, Inc., Warren, NJ, USA Lines: 20 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 133, message 7 of 9 In article , edw@wells.uucp (Ed Wells) writes: > > How does the caller ID work (technically)? Is it a DTMF code before > the phone rings? Some other kind of digital code? What ESS switch > does this feature start on? Caller*Id service is offered by NJ Bell using 1ESS and 1aESS switches. The calling number is delivered to the called party by a short blast of 1200 bps fsk data (similar, but not identical, to the modulation pattern used by 202 (half-duplex) 1200 bps modems). This occurs immediately after the first ring. It is not repeated after additional rings, nor is any ACK expected. In other words, it's simplex analog transmission, using 1960's modem technology. -- Dave Levenson /-----------------------------\ Westmark, Inc. | If you can't give me your | Warren, NJ USA | Phone number, don't call! | {rutgers | att}!westmark!dave \-----------------------------/