Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!casbah.acns.nwu.edu!nucsrl!telecom-request From: ccplumb@rose.uwaterloo.ca (Colin Plumb) Newsgroups: comp.dcom.telecom Subject: Re: How do You Hook up a Phone For a Play? Message-ID: Date: 20 Feb 91 00:11:21 GMT Sender: news@casbah.acns.nwu.edu Organization: University of Waterloo Lines: 51 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 137, Message 1 of 6 Originator: telecom@delta.eecs.nwu.edu John_Richard_Bruni@cup.portal.com wrote: > This may be hazardous to one`s health, but I have on several > occassions seen phones hooked up to [120 V] AC to ring the bell > for plays ... > [Moderator's Note: What you are suggesting is a *highly dangerous* > practice which could -- would !!! -- damage the phone beyond future > use to say nothing of hurting the hapless person who picked it up at > the wrong time. Don't do it! PAT] It's awfully presumptuous of me, but I'd like to suggest otherwise. Remember, we're talkking genuine Bell mil-spec 500 sets here. Indestructible by any means up to and including inquisitive young TELECOM readers. I'm quite sure raw AC would quickly turn any electronic phone into a puddle of plastic, but good old-fashioned mechanics isn't as fragile. Certainly the plastic on that nice solid handset is more than enough to keep 120V from my tender skin. The main danger is picking the phone up during a ring and thus connecting that line current to the speaker. I think that's a Zener in there protecting the speaker, but that won't last long. To allay everyone's fears, I suggest disconnecting the network before (ab)using a telephone in this way. My "500 12/77 Made in Canada" I have lying open in front of me has the line connecting to clips labelled L1 and L2 on the network (for non-techies, that's the little bit of circuitry in the phone. Three capacitors, one transformer, and two unidentified white boxes "1.5J250P" and ".12K250P"), which have leads to the ringer and other places. The L1 and L2 connectors are not connected to anything on the PC board, so just unplug the one extra wire from L1 and two from L2. You can stash them in the unused connectors E1 and E2 if you like. The ringer has four wires, the other two which go to A and K on the network. These are connected by PCB traces to a. .47/400V capacitor. It can probably take it... After this modification, the only thing you can fry is the ringer itself, and I'd be really surprised if that couldn't take a measly 100% overload. No, this isn't particularly good for the phone, but I've never seen theatre people worry about what's healthy. ("I'll be glad to spray-paint the backdrop with the ventilation fans out of order!") Colin [Moderator's Note: But more important, for their own personal safety you figure they will know enough to re-wire the network of the phone according to your instuctions? Mighty big assumption! PAT]