So, if I understand you correctly: For residential installations the telco generally have one pair hard copper directly from the CO to the home. They have a loopback/isolator at the CO, and a lightning arrester at the demarc. And that is all. No wonder I never saw one. Bob Ammerman RAm Systems ----- Original Message ----- From: "Larry Taylor" To: Sent: Monday, September 22, 2003 10:16 PM Subject: Re: [PIC:] Stealing power from the phone line update > BOB! The loopback is in the treatment card that interfaces with the phone > line to the customer equipment not in the Demarc. The Demarc is after there > equipment. That is normally power locally but can be powered from the Phone > Company. If this is at a home that little thing that the phone company wires > to is just a Lightning protector that goes to ground when there is a strike > that can be close to the phone lines. Treatment cards are used for looping a > 4 wire line. Tx on one pair and Rx on the other pair. This is used on Data > lines,Phone Trunks, not on a regular phone lines. Ring voltage 90 vac 20hz, > 48vdc minus line lost to phones. Phones look like 600 to 900 ohms.when its > off hook. They trigger the loop back with a tone 2817hz. > Larry Taylor KF6JBG Telecomm > ----- Original Message ----- > From: "Bob Ammerman" > To: > Sent: Monday, September 22, 2003 3:01 PM > Subject: Re: [PIC:] Stealing power from the phone line update > > > Hm... > > Never saw one around here, but it sure makes sense. > > I do have a demarc box a buddy just gave me. It is pretty recent. I'll have > to look inside. > > Any idea how they trigger it? > > Bob > > ----- Original Message ----- > From: "Vern Jones" > To: > Sent: Monday, September 22, 2003 3:44 PM > Subject: Re: [PIC:] Stealing power from the phone line update > > > > This isolation relay, or loop back relay is in the Telco Demark box in > > recent installations. This is used to let them know whether the trouble > > is yours or theirs. > > > > If your service hasn't been upgraded for 30 years, then you won't have > > one. > > > > Vern > > > > Bob Ammerman wrote: > > > > > > > In the states with Telephone offices equipped with MLT (most with > > > > electronic switches and former Bell companies), lines are normally > > > > tested 1 time each day, testing for line faults. If current is being > > > > drawn, it looks like a bad pair to MLT. > > > > > > > > They may look more closely using the isolation relay to determine > > > > whether it is the pair or your equipment. This could possibly generate > a > > > > letter to you requesting that you fix your equipment, or disconnect > it. > > > > > > > > Vern > > > > > > Where is this 'isolation relay'? I have never before heard about that. > > > > > > Bob Ammerman > > > RAm Systems > > > > > > -- > > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu