Path: utzoo!utgpu!cunews!bnrgate!brtph3!batpa1!cadnews
From: kahhan@bnr.ca
Newsgroups: sci.electronics
Subject: Re: Call number ID
Message-ID: <1991Feb17.145059.27092@bnr.ca>
Date: 17 Feb 91 14:50:59 GMT
References: <13147@hubcap.clemson.edu>
Sender: kahhan@batpa3
Distribution: na
Organization: none
Lines: 33

In article <13147@hubcap.clemson.edu> rbrink@hubcap.clemson.edu (Rick Brink) writes:
>OK, we all know what Caller ID is by now.  How about some quickminded programmer
>take the sting out of this for everyone.
>
>Why can't someone do the code to use one's computer modem to do the caller ID
>inquiry.  If it's a matter of the switchhood voltage drop, a simple circuit 
>should take care of that.  Surley these $125 boxes are just expensive tone
>encoders with a little memory.  I'd register a few dollars for a shareware
>program that does that.  
>
>(I think ol' ma' bell may have smelled this one, there is probably some very
>explicit reason why it can't be done, just the way they wanted it....)

One problem with using the modem to pick off the caller ID number is that
most computer modem operating at 1200 BPS use the 212 standard, while caller
ID from the telcos conforms to the old 202 standard. The modulation schemes
are entirely different, with 202 being FSK, while 212 is PSK. Unless your
modem is based on a DSP chip which can be reprogrammed via software off
the floppy disk, this does not represent a viable solution.

On the other hand, building a decoder is not that difficult. Standard ICs
are readily available (AMD has their "world chip") which can implement
the 202 standard. I would expect that we'll soon be seeing kits and
or low cost devices available shortly. In the near term, this could be
a good business opportunity, until the Japanese ramp up production and
start selling them for $15.

-- 
----------------------------------------------------------------------------------
Larry Kahhan - NRA, NRA-ILA, CSG, GOA, GSSA |   The opinions expressed here do
                                            |   not necessarily represent the
                                            |   views of the management.
----------------------------------------------------------------------------------