As you and I said
"the receive has no means of signaling or handshaking to the co line"
Don
.
Larry wrote:
Donald Ritchie wrote:
The thing I wonder about, that doc is like 15 years old, and while it
explains incoming CID
it said nothing about CID delivery on a "call waiting" call.
I wonder if anybody REALLY knows how this works ?
cwcid- the co outbound audio path is opened, cwtone is sent followed by
bell 202 equivalent data stream then the path restored.
for regular cid, 1/2 second after end of first ring, co path opened,
bell 202 data stream sent, path restored.
the cid receiver is coupled to the co line with two 100k resistors in
series with two .01mf caps. That circuit has REN = 0 and will easily
withstand 90v ring voltage. the receiver will sync and receive the data
steam after "hearing" the alternating 1/0 preamble tone pattern. the
receive has no means of signaling or handshaking to the co line.
the original receivers used the ring voltage cycle as a "wake-up" signal
to save power. the new circuits are low power cmos and listen all the
time. you can spoof caller-id by sending your "own" cid stream just
after answer (overwrites prev display - still in mem though). you can
send the tone anytime, but voice component tends to tear up fsk stream.
Original co used relay to drop loop and add 202 modem, co had to be
"conditioned" for insertion. the modems were shared common equipment
and were only connected to a line for a little over 1 sec. most recent
computer modems can receive cid by setting an "at" cmd like #CID=0
(thru 3) 1/2/3 is raw, ascii, formated.
most still use the ring cycle to "pull" the dial pulse reed relay to
connect the modem chip "playing" a bell 202 receiver. latest ones can
do cwcid as well.
Carl should be in here, he put in his time at a co ;-) [btw my fav was
the MCXI lines!]
i would wonder if pano has enough transmitters to send that much cid.
the kxtd with a 171 only had 1 channel. not enough shared equipment.
has it ever worked?
(never touched a ta)
go buy your own bellcore ;-)
-l
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