On Thu, 16 Jul 1998, Russ Blakeman wrote:
> The caller id info rides as a carrier on the line too at a different
> frequency than the voice signal so that only the id box (and similar
> instruments) can read it. If I'm not mistaken it's sent as a 300 baud
> carrier. The way it senses the ring is the increase in DC line voltage from
> an average 35vdc to around 80vdc, telling itself to look for and recieve a
> data string which includes time and date.
When a phone is on-hook (hung-up) there is a 48V potential on the line.
When the phone is ringing, there is 90v (nominal) AC on the line during
the ring cycle to activate the ringer. When a phone is off-hook (you're
talking) there is 12v on the line.
Sam Alternate e-mail: dastar_at_siconic.com
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Received on Thu Jul 16 1998 - 12:25:10 BST