Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!hayes.fai.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request From: john@bovine.ati.com (John Higdon) Newsgroups: comp.dcom.telecom Subject: Re: Supervision / Call Forwarding No Answer Message-ID: <12960@accuvax.nwu.edu> Date: 2 Oct 90 18:07:22 GMT Sender: news@accuvax.nwu.edu Reply-To: John Higdon Organization: Green Hills and Cows Lines: 39 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 706, Message 11 of 13 On Oct 2 at 2:40, Steve Elias writes: > What do LD carriers do when they dial a number that the destination CO > has programmed as a "call forward - no answer", and the number > forwarded to is busy? In this situation, the caller hears a few > rings, and then a busy signal. Surely this will confuse people who > call me and don't know that I'm a telecom weirdo... But what about > the "supervision" return codes to the originating CO? If someone > calls long distance and this happens, will they get billed because of > the change in cadence from ringing to busy? Steve, as a telecom weirdo (TM), you must be aware that long distance companies (including Sprint) use the traditional supervisory signal that is not related in any way to what is happening on the audio path. When the distant phone is actually answered, the distant CO notifies the originated CO ALL THE WAY through the IXC (if one is used) via positive means that depends not on any sound made at the distant end. In the old days, this was represented by a reversal of battery on the line or inter-office trunk. In the days of long distance MF signaling, removal of 2600 Hz indicated supervision or "reversal". Now, of course, supervision in indicated through the CCIS control channel. Those two-bit LD companies that still "guess" at supervision generally use a simple timeout -- if the customer stays on the line for more than a preset limit, then supervision is assumed. I'm aware of none that actually "listen" for an answer. Actually, that would be superior to a timeout. In the case of COCOTs (that DO listen for stuff on the line), this would probably not confuse them. Most "listening" COCOTs check for the asymetrical signature of the human voice. A mixture of ringing and busy (both pre-supervision sounds) would probably not result in your coin being collected. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@bovine.ati.com | San Jose, CA 95150 | M o o !