Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!bellcore!texbell!vector!telecom-gateway From: claris!edg%bridge2.ESD.3Com.Com@ames.arc.nasa.gov (Ed Greenberg) Newsgroups: comp.dcom.telecom Subject: Re: Loud hum on the Phone Message-ID: Date: 9 May 89 04:19:52 GMT Sender: news@vector.Dallas.TX.US Reply-To: Ed Greenberg Organization: 3Com Corp., Mt. View, CA Lines: 47 Approved: telecom-request@vector.dallas.tx.us X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@vector.dallas.tx.us X-TELECOM-Digest: volume 9, issue 159, message 4 of 8 In article russ@silver.bacs.indiana. edu (Jeff Russ) writes: >My telephone recently started acting up. When I pick up the phone I hear >a loud hum. >... middle deleted > ... there >was a thunder storm with lots of lightening before I noticed the problem. >I'd appreciate any suggestions as to what to check before I call the phone >company. > Jeff Russ My guess is you've blown a carbon protector. This happened to my family when I was about 18 years old (15 years ago) and it was a major pain in the *ss because I had the house full of then "illegal" phones. You need to (a) unplug all the phones and other telephony equipment in the house, (b) find the demarcation point where the line enters and (c) test the line there. If it still acts up, call the telco. What's going on is this... Theres a block where the phone line enters which has two carbon inserts connected to ground. These protectors are supposed to short to ground when lightning or other transients strike. If one blows, you've got a grounding problem. This causes the hum. The carbon block will be found in the basement, garage or on the wall outside the house. It will have two screw or bolt down terminals, and two other screw covers containing the carbons. The outside wire will be connected to the two bolt-down terminals. The inside wire will also be connected to those terminals. There will also be a ground which will be grounded (or "earthed" as our friends in the UK say.) If your house is new, there will also be a modular "demarcation point" which defines where telco responsibility ends and house wiring begins. If so, unplug the demarcation jumper and plug a phone into "their" side. If it hums, call them. If it don't you've got another problem, probably a grounding problem inside the house. Good luck, and let me know if I was right. -edg -- {decwrl|sun|oliveb}!CSO.3com.com!Edward_Greenberg Ed Greenberg -or- 3Com Corporation {sun|hplabs}!bridge2!edg Mountain View, CA 415-694-2952