"Andrew A. Houghton" <ah0i+@andrew.cmu.edu> (07/13/90)
In brief, I have heard that at one time AT&T sent out "cleaning pulses" in the wee hours of morning to "fuse shorts in the line." Assuming this is drivel, is there any basis for such a thing? Just wondering, Andrew Houghton (ah0i@andrew.cmu.edu)
mingo@uunet.uu.net (Charles Hawkins Mingo) (07/16/90)
In article <9677@accuvax.nwu.edu> ah0i+@andrew.cmu.edu (Andrew A. Houghton) writes: >In brief, I have heard that at one time AT&T sent out "cleaning >pulses" in the wee hours of morning to "fuse shorts in the line." "At one time?" I get half second chirps on my AT&T phone around 1 AM, usually once or twice a week. I had assumed it was the local phone compant (C&P) since they had warned me of middle of the night interruptions in service last March, when they apparantly replaced the local switch. It sounds like someone is phoning you, and changing their mind real quick (fraction of a ring). Charlie Mingo Internet: mingo@well.sf.ca.us 2209 Washington Circle #2 CI$: 71340,2152 Washington, DC 20037 AT&T: 202/785-2089
knop@duteca.tudelft.nl (P. Knoppers) (07/16/90)
In article <9677@accuvax.nwu.edu> ah0i+@andrew.cmu.edu (Andrew A. Houghton) writes: >X-Telecom-Digest: Volume 10, Issue 479, Message 5 of 14 >In brief, I have heard that at one time AT&T sent out "cleaning >pulses" in the wee hours of morning to "fuse shorts in the line." >Assuming this is drivel, is there any basis for such a thing? Yes and no... The yes part: Phone companies (at least in The Netherlands) regularly test subscriber lines using voltages up to several hundreds of Volts. Subscriber equipment is designed to survive such tests. The tests are carried out with no (or almost no) human supervision. Lines that happen to be in use during the test are skipped. The no part: I don't think that the phone company expects to cure faults in the isolation of the subscriber loops. It might work for a while if you are lucky, but the line will never become reliable again. The aim of these test is to detect problems before regular service is hampered. P. Knoppers, Delft Univ. of Technology, The Netherlands, knop@duteca.tudelft.nl
npl@mozart.att.com (Nickolas Landsberg) (07/16/90)
In article <9677@accuvax.nwu.edu> Andrew Houghton writes: >In brief, I have heard that at one time AT&T sent out "cleaning >pulses" in the wee hours of morning to "fuse shorts in the line." >Assuming this is drivel, is there any basis for such a thing? >Just wondering, This comes up periodically, so let me dust off the old brain cells and try to come up with a semblance of the truth - All(?) Electronic switches and most electro-mechnical switches can be programmed to run a test or series of tests on the subscriber loop. Generically, these are called Automatic Line Insulation Tests (ALIT). There are three types of tests which may be performed: FEMF (Foreign EMF, a.k.a. Cross Battery), SRG (Short and Ring Ground), and TRG (Tip and Ring Ground). The one which I am most familiar with (being an old Outside Plant type) is the FEMF. In theory, especially if paper insulated cable is still in use, any moisture in the cable will condense at night and reduce the insulation resistance. Moisture will tend to congregate at a low spot in the cable, thus reducing the resistance of a number of subscriber pairs at once. This argument is probably specious in PIC (Plastic/polyethelene ? Insulated Cable. Running the tests also competes with providing dial-tone, thus, the switches are programmed to run the test at night. The telephone number of lines which failed the test are printed out on the maintenance channel of the switch. In some companies, this channel is also monitored by yet another computer system which translates the telephone number to cable & pair, and, in some cases performs yet another test to verify that the condition is still there. The voltage applied during testing has nothing to do with "cleaning pulses" or to "fuse shorts on the line." About the only thing I saw which would "fuse shorts" is a "630" set. (630 Volts DC applied to the line.) P.S. Does anyone know if these are still in use? It's been years since I left the Outside Plant Dept. Nick Landsberg