Path: utzoo!telecom-request Date: Mon, 10 Jun 91 20:53 PDT From: John Higdon Newsgroups: comp.dcom.telecom Subject: Re: Rotary Dial Phones Forgotten But Not Gone Reply-To: John Higdon Message-ID: Organization: Green Hills and Cows Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 450, Message 3 of 11 Lines: 22 Julian Macassey writes: > The voltage applied to the Tip and Ring to activate the light is > usually 90V at 100Hz. This frequency is ignored by the frequency > sensitive ringer that responds to 40 - 150V at 20 Hz. The neon is not > frequency sensitive, so it flashes for message waiting or ring > current. ITT uses a similar, but much simpler method of lighting the message waiting lamp. The System 3100 just sends 60 ipm pulses of 100VDC over the line. The direct current is completely ignored by the ringer, but lights the neon lamp. Unlike the 100Hz, there is no flow through any circuitry except for the neon lamp. In addition to being much more difficult to generate (than DC), some of the 100Hz will inevitably leak through the L/C bell network creating a bit of inefficiency. The DC supply is very simple and cheap. John Higdon | P. O. Box 7648 | +1 408 723 1395 john@zygot.ati.com | San Jose, CA 95150 | M o o !