Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!apple!julius.cs.uiuc.edu!zaphod.mps.ohio-state.edu!casbah.acns.nwu.edu!accuvax.nwu.edu!nucsrl!telecom-request From: john@bovine.ati.com (John Higdon) Newsgroups: comp.dcom.telecom Subject: Re: Phones and Radio Broadcasting Message-ID: <15614@accuvax.nwu.edu> Date: 22 Dec 90 18:05:19 GMT Sender: news@accuvax.nwu.edu Reply-To: John Higdon Organization: Green Hills and Cows Lines: 27 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 899, Message 2 of 10 "David E. Bernholdt" writes: > Can anyone tell me why once the connection was completed the line > would be so clear? I have no idea if there were any special filters > on the phone or anything like that. This was about ten years ago, if > that makes any difference in technology/equipment. Mechanical switching equipment (particularly crossbar) is notorious for imbalancing the customers line while accepting digits. When the call completes, the customer is connected to an intra or inter CO trunk unit which presents the proper load and longitudinal balance to the line. A properly balanced audio line is much less suceptible to any type of external interference (including RF). That is why radio stations are very careful to use balanced audio circuits if the studio is co-located at the transmitter. (And why consumer audio gear is so suceptible with its unbalanced audio cables.) I remember some relatives that lived some distance out of Bellevue, WA, that had a phone served out of a #5 crossbar office. The hum on the line was deafening during dialing, but it would go away with the "ka-plunk" that came after dialing. Originating registers are apparently a very bogus termination. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@bovine.ati.com | San Jose, CA 95150 | M o o !