Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!netsys!vector!telecom-gateway From: julian@bongo.uucp (julian macassey) Newsgroups: comp.dcom.telecom Subject: Re: Buggy lines Message-ID: Date: 10 Jul 89 00:51:51 GMT Sender: news@vector.Dallas.TX.US Organization: The Hole in the Wall Hollywood CA U.S.A. Lines: 35 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 228, message 5 of 7 In article , claris!wet!epsilon @ames.arc.nasa.gov writes: > I have one of those GE multiline phones with the line-monitoring > LEDs; each day around 0200 (the exact time varies) they flicker > briefly. (415-337) Counting RENs? :-) They flicker because the telco is testing the loop (Your line to the Central Office). The lights should not flicker if the phone actually met FCC Part 68 and Bell Pub 48005 and the GTE equiv the number of which escapes me right now. The phone when On Hook should have a DC resistance above 10 Meg Ohm and a particular on hook impedance. Exact numbers escape me, but without getting too techie let me explain what is expected. A phone on hook should present a 0.47 uf Capacitor and a large coil of wire in series to the loop. This means a gong ringer and the DC blocking capacitor. Most ringer ICs (the ones that chirp and warble) do not present this impedance curve to the phone line. The Motorola ones do and I think the AT&T ones may. No one ever gave me AT&T phone ICs to play with. Now the lights on the GE phone are possibly controlled by Zener diodes that turn on the lights when the DC voltage drops below say 26 Volts. The normal on hook voltage is 48 V and off hook it will drop to about 9 to 3 V. When testing the telco may lower the line voltage and your lights may flicker. They also sometimes use low frequency and low voltage test sigs. Maybe someone at the CO side of biz could supply us these specs? The Telco would probably love you if you junked the phone and got a real one so they could get meaningful test results. Yours -- Julian Macassey, n6are julian@bongo ucla-an!denwa!bongo!julian n6are@k6iyk (Packet Radio) n6are.ampr.org [44.16.0.81] voice (213) 653-4495