At 06:14 PM 6/12/2006, 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!]
He's here, but he left the telco in 1980 and we got the GTD in 1985 and CID in 1988 or shortly thereafter. The GM had it, but the rest of us didn't see the "tarrif" until it was "debugged". Or some such crap. Carl :what's a Bellcore gonna do for us" Navarro _________________________________________________________________ KX-T Mailing list --- http://kxthelp.com/ Subscription changes: http://kxthelp.com/mailman/listinfo/kxt
