ee5391aa@hydra.unm.edu (Duke McMullan n5gax) (05/03/89)
In article <3139@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > Sorry, but you canNOT ring a phone with "house current". Virtually >all conventional telephone ringers are frequency selective, and operate only >between 16 and 32 Hz; 60 Hz won't cut it. Some ringers used on older >party line systems (like the "harmonic", "decimonic" and "synchronic") were >_very_ freqeuncy selective, with a "bandpass" of 5 Hz or less. Wellll -- I do it on occasion. I generally pull the voltage down to about 90 VAC with a variable autotransformer for safety, but the 'phone rings loudly and continuously. If you close the hookswitch, you get a loud buzz. ;^) I've never tried it on one of the new solid state (easily damaged, cheap, poorly made, etc., etc.) 'phones so widely available, but ALL of the old-style Western Electric sets I've tested (just under a dozen, I'd imagine) ring just fine at 60 Hz. The ring does seem a little "buzzy" or rapid, as you'd expect. I don't speak for every 'phone, but you can ring _some_ of 'em with 120VAC. Call me a 'phoney, d "To be or not to be -- that is the square root of 4 B^2." -- Anon. Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu
larry@kitty.UUCP (Larry Lippman) (05/05/89)
In article <5012@charon.unm.edu>, ee5391aa@hydra.unm.edu (Duke McMullan n5gax) writes: > > Sorry, but you canNOT ring a phone with "house current". Virtually > >all conventional telephone ringers are frequency selective, and operate only > >between 16 and 32 Hz; 60 Hz won't cut it. Some ringers used on older > >party line systems (like the "harmonic", "decimonic" and "synchronic") were > >_very_ freqeuncy selective, with a "bandpass" of 5 Hz or less. > > Wellll -- I do it on occasion. I generally pull the voltage down to about > 90 VAC with a variable autotransformer for safety, but the 'phone rings loudly > and continuously. Well, I suppose anything is possible if you drive the ringer hard enough. Ringing voltage as provided from central office apparatus is well limited as to current. For many years the method of current limiting was a resistance lamp; this method was also used in earlier ESS systems. Newer apparatus uses solid-state current limiting circuits, although resistance lamps are still used in some apparatus because they are so _simple_ and reliable. A WECO 13G resistance lamp was typically used for current limiting on ringing circuits and has a current limit of around 400 mA. At a typical 20 Hz ringing voltage of 100 VAC, a 500 ohm subscriber loop would of itself limit ringing current to 200 mA. In addition, the central apparatus trunk circuit introduces further resistance from the ring-trip relay or series resistor used for electronic current sensing. Ringing current is further limited by a series capacitor in the telephone set itself to 50 mA or less. A typical mechanical ringer is well intentionally designed for frequency selectivity though the use of a careful core design, a permanent magnet for magnetic bias, and an adjustable spring for mechanical bias. I don't doubt that it will ring to 60 Hz if you drive it hard enough to overcome the magnetic and mechanical bias elements. Under the circumstances, I bet you were either: (1) driving the ringer at current levels >> greater than 50 mA, and/or (2) driving the ringer without the usual series capacitor. > If you close the hookswitch, you get a loud buzz. ;^) See any smoke? :-) <> Larry Lippman @ Recognition Research Corp. - Uniquex Corp. - Viatran Corp. <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231, 716/773-1700 {att|hplabs|utzoo}!/ <> FAX: 716/741-9635, 716/773-2488 "Have you hugged your cat today?"
ISW@cup.portal.com (Isaac S Wingfield) (05/06/89)
When I was in College, I did a lot of technical theatre work; one of the things we never could "realistically" record and play back was the sound of a ringing phone on stage. We regularly rang standard issue phones from the power line. (We always wired the ring voltage through the hook switch, and instructed the performers to pick up "during a ring"; it was more realistic that way). Of course these were POTS phones, probably 500 series. Isaac isw@cup.portal.com
vermilye@penelope.oswego.edu (Jon R. Vermilye) (05/11/89)
In article <3144@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <5012@charon.unm.edu>, ee5391aa@hydra.unm.edu (Duke McMullan n5gax) writes: >> > Sorry, but you canNOT ring a phone with "house current". Virtually >> >all conventional telephone ringers are frequency selective, and operate only >> Wellll -- I do it on occasion. I generally pull the voltage down to about >> 90 VAC with a variable autotransformer for safety, but the 'phone rings loudly >> and continuously. > > Well, I suppose anything is possible if you drive the ringer hard >enough. > Under the circumstances, I bet you were either: (1) driving the >ringer at current levels >> greater than 50 mA, and/or (2) driving the >ringer without the usual series capacitor. > >> If you close the hookswitch, you get a loud buzz. ;^) > > See any smoke? :-) I have to add my 2 cents. We have been ringing phones with 60 Hz AC for years. I just finished measuring the ringing current on a standard C/D 500 (old black non-electronic) phone - 40ma. Of course the ring is not normal, but it does ring, and the current is reasonable. The best solution for ringing phones for the theatre is to get a ringing generator. We use a Tellabs 8101, which produces 90 - 120 v AC at 30Hz. The phone will sound normal and the ferro-resonant saturable core reactor limits the output to about 5 watts. It cost about $60.00 in 1980, and since it is is a mechanical, ie transformer, device, it puts up with the abuse that theatrical technicians can provide. By the way, if you plan to answer, ie pick up the reciever of the phone, be sure to remove the earpiece. You don't have the CO to shut off the ringing voltage, and 30 or 60 hz at ringing current will annoy the actors ;^). I also suggest that you modify the phone so that lifting the handset will open the ringing circuit. You can use some of the normally closed contacts on the hanger switch. This will prevent the situation where the phone is ringing while the actor holds it in his hand. I suspect that many of these modifications swould be more difficult on an electronic phone, however is should still ring with the ringing generator. Jon R. Vermilye 315 341 2138 Department of Theatre vermilye@oswego.Oswego.EDU SUNY Oswego rutgers!sunybcs!oswego!vermilye Oswego, NY 13126