🚀 go-pugleaf

>	So, theoretically, one could modify and old 1200 baud modem to use the
>modified tones (or even just pass the signal through some kind of filter to
>transform the tones to normal 1200 baud tones) and have caller ID for free?

Caller-id is sent as as 1200 baud signal (I think it's Bell 202 which is
pure FM, not bell 212 as usual 1200 baud).  And it's done while
ON hook (regular modems are ment to operate only off-hook).
The data is tramsmitted between the first and second rings.
If you pick up ANY phone too early, the data transmission is
aborted and there's no way for you to re-request it.

With caller-id chips such as the Motorola or Sierra being free of under
US$3, why bother modifying a modem when a module from scratch is cheaper?
There are too many modifications needed to shoehorn an old modem to
caller-id (different modulation, and the different voltages of
being ON hook / still hung up).

>	BTW, when I say free, I mean in the sense that I wouldn't have to go
>out and by a caller ID phone, since I'd still have to subscribe to get
>the information coming down the line.

True enough, the caller id is NOT transmitted to you, the subscriber,
unless you pay for it.  You've got to subscribe to the service
to get it (just as with call waiting, etc).
-- 
Jeffrey Jonas

jeffj@panix.com