bernhold@qtp.ufl.edu (David E. Bernholdt) (12/21/90)
In article <15512@accuvax.nwu.edu> motcid!segal@uunet.uu.net (Gary Segal) writes: >X-Telecom-Digest: Volume 10, Issue 890, Message 7 of 11 >A former friend of mine in >Bloomingdale Illinios had the unfortunate problem being served by a CO >that is close to the transmit tower for a FM radio station. Somehow >the radio program found it's way into the local loops. >[Moderator's Note: Sometime take a drive out near Wheaton, IL where >two powerhouse radio stations (WGN - 720 AM and WBBM - 780 AM) have >their transmitters within about a quarter-mile of each other. >All the telephones in the area have special filters on them provided by IBT. There is also a WBBM/AM transmitter in Elk Grove Village, IL. A friend of mine lived (essentially) across the street from it. When you picked up his phone, you heard WBBM instead of a dial tone, but once you dialed an made a connetion, the line was quite clear. 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. P.S. He could also get WBBM on his toaster. Lots of RF around there! David Bernholdt bernhold@qtp.ufl.edu Quantum Theory Project bernhold@ufpine.bitnet University of Florida Gainesville, FL 32611 904/392 6365
john@bovine.ati.com (John Higdon) (12/23/90)
"David E. Bernholdt" <bernhold@qtp.ufl.edu> 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 !