Allison J Parent wrote:
<If the caller ID data signal was sent first, it
would cause jittering in
< mechanical ringers, and a maddening noise in electronic ones. When the
< ring is detected, the caller ID can 'pick up' the phone line briefly to
< check the data signal, which should be extremely brief. The station
< knows to keep ringing the phone if the user has caller ID. This is my
Wrong.
Caller id senses the ring and does not go off hook as that would disturb
the CO and it is uneeded. Instead the ring is an alert to the caller ID
that data will follow and it's already camped on the line using a non-DC
(capacitor coupled) connection to avoid loading the line. this allows
it to hear the ring and the data.
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.
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Russ Blakeman
RB Custom Services / Rt. 1 Box 62E / Harned, KY USA 40144
Phone: (502) 756-1749 Data/Fax:(502) 756-6991
Email: rhblake(a)bbtel.com or rhblake(a)bigfoot.com
Website:
http://members.tripod.com/~RHBLAKE/
ICQ UIN #1714857
AOL Instant Messenger "RHBLAKEMAN"
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