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From: ror@grassys.bc.ca (Richard O'Rourke)
Newsgroups: sci.electronics
Subject: Re: telephone Caller ID
Summary: Checksum
Message-ID: <167@grassys.bc.ca>
Date: 4 Jan 91 04:48:16 GMT
References: <1991Jan2.183802.13412@amd.com> <1991Jan3.163735.23511@zoo.toronto.edu>
Organization: Grass Root Systems, Burnaby, B.C., Canada
Lines: 16

In article <1991Jan3.163735.23511@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes:
>In article <1991Jan2.183802.13412@amd.com> lpdjb@brahms.amd.com (Jerry Bemis) writes:
>>How is the caller ID encoded on the phone lines?
>
>It's one of the old 1200-baud modem encodings, I think.  You get it only
>once, and there is no parity or other error detection/correction.

There is a checksum.  If the CID box gets a failed checksum it is
supposed to ignore the data and not display a number.
> 
> "The average pointer, statistically,    |Henry Spencer at U of Toronto Zoology
> points somewhere in X." -Hugh Redelmeier| henry@zoo.toronto.edu   utzoo!henry

-- 
Richard O'Rourke: (604)438-8249  | Grass Root Systems: 436-1995
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