Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!mips!decwrl!hayes.fai.alaska.edu!accuvax.nwu.edu!nucsrl!telecom-request From: 0004133373@mcimail.com (Donald E. Kimberlin) Newsgroups: comp.dcom.telecom Subject: The Truth About "Cleaning Pulses" Message-ID: <9742@accuvax.nwu.edu> Date: 15 Jul 90 01:42:00 GMT Sender: news@accuvax.nwu.edu Organization: Telecommunications Network Architects, Safety Harbor, FL Lines: 54 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 485, Message 6 of 6 In article , Andrew 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? Yep, Andrew, it's more of the drivel that gets made out of stories told and retold by telecommunications incompetents. Like all, it has a shred of truth ... but only way down and way back. Hear this: For starters, AT&T _never_ sent out "pulses" down your local line. Your local exchange telephone company does that. AT&T did, of course, own the twenty-plus local "Bell Operating Companies." These were, in no uncertain terms, captive customers of Western Electric, AT&T's manufacturing company, which in turn had only technology of Bell Labs to sell. So, if Bell Labs dreamed up an improvement to running local phone lines, the Bell companies bought it. A well-recognized problem in running local phone lines is: How does one indeed know when a phone line is bad? Wait for the customer to get to another phone and call? With all good intent, AT&T HQ put this on Bell Labs' plate. Bell Labs came up with an adjunct to its Crossbar-era exchanges (we're talking 1950's technology here) called Automatic Line Insulation Test ... ALIT in the trade. The earliest ALITs were totally mechanical, and scanned the office during wee hours, putting a fairly high-voltage (limited current) pulse on the line to measure the leakage resistance of the wire pair, flagging those in which the leakage was lower than the acceptable level; printing a report, in fact, for the local people to "fix your line before you knew about it." Those are the "pulses," but they don't "fuse the shorts in the line." Somewhere down the story trail to you, the incompetents have mushed ALIT together with the old testboardman's trick of "burning" a noisy pair's loose splices or tree branches of long-gone open wire with about 600 Volts for a moment. ALIT doesn't do that. It just measures. ALIT lives today and is now an electronic "test adjunct" to most every telephone exchange switch. It is even a popular manual test method, called up by remote control to get an evaluation of the condition of your wire pair when you do say the line is "noisy" or "weak." There are test criteria and a large backgound of use of the techniques of ALIT, used by every telco. BUT, honest, dirty truth be known, very few ALITs are running all night to check out your line for you. The local plant people dropped the administrative task of keeping ALIT in automatic operation years ago. If you live in GTE areas, you'll find they now run TX spots showing people snoozing away in bed, happily confident that GTE is "testing their lines silently all night." All that happened was GTE started its ALITs back in automatic mode again! So much for "AT&T pulses that clean your line!"