Path: utzoo!telecom-request Date: 9 Jun 91 18:17:23 GMT From: Julian Macassey Newsgroups: comp.dcom.telecom Subject: Re: Rotary Dial Phones Forgotten But Not Gone Reply-To: Julian Macassey Message-ID: Organization: The Hole in the Wall Hollywood California U.S.A. 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 444, Message 10 of 10 Lines: 45 In article nstar!bluemoon!sbrack@ iuvax.cs.indiana.edu (Steven S. Brack) writes: X-Telecom-Digest: Volume 11, Issue 433, Message 8 of 13 > On our NT SL100 PBX, the individual 2500 sets have a "tap" button, > which, pressed once, sends a flash of the correct length. It seems to > be some sort of capacitor arrangement, but since OSU is more paranoid > than ATT about people opening up their phones, I haven't investigated. It is actually a Motorola IC. I have the schematic for these Comdial phones somewhere, buried with schematics for Yugoslavian phones etc. I can't find it now, but I did discover lots of neat stuff I haven't seen for a while. This circuit the "TAP telephone" was as I recall designed by Joe Flamini, a real telecom character. He is an MIT Phd, ex cop, bon vivant and comedian. Anyhow, the IC is a Dual Timer. One half sets up the flash button for a 600Ms break and the other half, which is across the hookswitch is set up for 1500 Ms. This is why when you try to flash the hookswitch on the TAP phone you hang the phone up. Comdial sold a ton of these things to ROLM who installed them as "ROLM Phones". They are still available as Comdial TAP phones from your local telco distributor. They come with or without the message waiting light. > The tap button also houses the voicemail waiting lamp. This lamp also > lights when ring current is applied to the instrument. What is the > relation between the light and the ringer? The "voicemail waiting lamp" is called the message waiting light. It is most often seen in hotel rooms. In hotels when they have a message for you, they turn on the light. This is done automatically with voicemail. The light is a neon with a 100K resistor in series. 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. Julian Macassey, julian@bongo.info.com N6ARE@K6VE.#SOCAL.CA.USA.NA 742 1/2 North Hayworth Avenue Hollywood CA 90046-7142 voice (213) 653-4495