Telephone Ringers: how & why

Years ago, I read an explanation of why telco ringers are what they are. [Or ...were..., now that we are doomed to tweedlers...except @ my house where the 2565 lives on forever...]

Yea, we know that they are typically 20hz, sinusoidal waveform, ~120VAC RMS atop 45VDC....

But... the WHY behind those decisions was illuminating. After all, there's a fair chunk of change in that dual gong ringer's magnetic design, etc...

The explanation had to do with the issue of coupling enough energy down a twisted pair tens of thousands of feet long, with 2R series resistance and Xc capacitive reactance shunting things.

I have no idea where I read this; it could have even been a Larry Lippman post, but I don't find anything in a brief search.

Does anyone here recall something on this?

Reply to
David Lesher
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Sure, that's what it was about. That was also why all phones at one's house had to be declared, and their "ringer equivalency number" and ampere rating. Folks at the very end of a such a line didn't have much juice left to actually actuate the ringer, which was an electro-magnet pulling a flat plate against the end of the coil/pole combo, then releasing it. The bell rang one tone on the pull, which required the power, and ALWAYS would ring the other on release.

Reply to
ChairmanOfTheBored

And that very same 90VAC 20Hz ring signal meant that the first electronic switching system deployed in Morris, IL need custom phones with electronic ringer because the gas tubes couldn't handle the high voltage necessary to pass ring. They overcame that with the Remendur switches but it took time.

Reply to
T

The stuff I have always worked with was 48vdc and 90vac, and the 90vac was not always sinusoidal, but close.

TerryS

Reply to
Terry

Well, in theory 48V, [my typo..] but in reality above that in float, and even more in equalize...

My SubCycle provides ~110Vrms unloaded....

Reply to
David Lesher

Also, remember, that there were several frequencies available for ringing, to allow for party lines. Each home had a different frequency ringer, so one could be distinguished from the other. In the CO, they had to manually wire the correct ringing frequency to that line.

Charlie

Reply to
Charlie Edmondson

Not all telcos used frequency selective ringers. Bell was, I believe, 20 Hz. I know United Tel, General Tel, and many smaller companies used FS ringers.

Reply to
Don Bowey

Not in Bell. They used tip party/ring party; and the gas tube bias scheme.

GTE and independents used various frequency selective schemes. There were at least 3.

This ties back to my original, unanswered, question. Straight line ringers were not tuned. Yet they somehow resonated.....

Reply to
David Lesher

Well, since I was working for GTE at the time... 8-)

Charlie

Reply to
Charlie Edmondson

They are capacitively coupled to the line, so they alternated between different directions due to the ringing frequency. They didn't have to resonate at all...

charlie

Reply to
Charlie Edmondson

I once read something, not about the electric part, but that the bell frequencies, and clapper rate, were specifically chosen to be "an 'impatient' sound", i.e., as annoying a sound as they could make with the technology of the day.

Cheers! Rich

Reply to
Rich Grise

But the impedences of the ringer are optimized for 20hz I bet. And why 20hz ? I don't remember.

TerryS

Reply to
Terry

Then they should have had it play country music.

;-)

Yes, Cheers !

Reply to
John Agosta

An old-time telephone engineer once told me the same thing. Might be some truth in it.

LOL! Hear, hear!

Tom

Reply to
Tom2000

The irony is that actual ringing-clapper phones are not in service anymore. Modern electronic phone apparatus, whether a telco, a PABX, or a small LinkSys VoIP module, has to create this ancient high-voltage ringing signal, and then a modern electronic phone has to respond to it, by creating a logic signal or whatever, and thereafter making its own ringing indication. How awkward.

The Institute's PABX, the second one we've purchased since I arrived 19 years ago, has started acting up - four or five of the lines have weak or defective ringing outputs, so those phones don't ring, or do so unreliably. The PABX uses 8-line cards, each one apparently with its own ringing generator. But replacing what appeared to be one defective card only partially solved the problem. We've just placed a new PABX on order, but it won't be installed for a month or so, and so we may need to make emergency repairs to the old one. No schematics are available, of course. But at least the circuits use ordinary components, SFAICT, from a quick look at the defective card last night. How awkward.

The putative ringing-generator circuit sports a classic '3842 PWM chip. I don't know if that's awkward or not. I say that, because it doesn't appear to be simply used as an ordinary high-voltage DC generator, because there are no other power parts, as would be needed to make a class AB HV amplifier, etc. There is one transformer.

Reply to
Winfield

Sure they are. I've got one plugged in at home, and there's one here at work as well. OK, the on at work is only "in service" if the PBX is powered down, but it's there...

Reply to
Grant Edwards

Winfield wrote in news:1187778109.632085.68860 @x40g2000prg.googlegroups.com:

Its all because they have to be backwards compatible to the old phones. The not-so newer phones were made to work alongside onlt mechancial ringer phones. Ihave here some early 90s phones that could have been used alongside the old 500 set we had.

Reply to
Gary Tait

I've got about fifty analog ports available on my Prologix so they do push 90VAC/20Hz down the line for ring. If you look at the cards you'll see they use a relay to switch between the talk path and ring current.

Reply to
T

In the very beginning they realized there was a need to signal the caller and the operator. Thus the ringer. To power the ringer, the subscriber had a hand crank. I believe originally the frequency was

16 Hz, then later to 20 Hz. These were known as local battery systems. The subscriber's telephone set had batteries in it. The advtg of these systems was that worked well on lousy loops, either very long ones or ones made of poor conductors (like fence posts).

On today's common battery systems, where the talking current is supplied by the phone company, the ringer must be AC to be separate and cut out, via the capacitor, so it won't shunt the line and appear off hook. (Others can explain this better.)

In the old the days the Bell System knew how many extensions a subscriber how since it provided them. I could ensure adequate ringer power was available. Very few people had more than five extensions on a single line.

But later people no longer had to rent their phones and could buy them. A way was needed to avoid overloading the line, so a "ringer equivalence" was set up. The plain Bell System 500 set was defined as

1.0 . As it turned out, most newer sets had a lower rating, my Comdial 2500 with a mechanical ringer is 0.8, electronic ringers are even less.

Would anyone know what the ringer equivalence be of older phones, such as a 300 set or the Bell Chime?

I don't know if this system is used on all-new PBXs that have digital phones, perhaps they use a different signalling technique altogether. Obviously VOIP isn't shooting 20Hz 90VAC over the Internet.

Someone mentioned Morris IL, yes, they had to develop a low powered tone ringer. But it didn't work out very well and was not continued. ESS was developed to handle standard ringing. How it's done today with digital switches I don't know.

Reply to
hancock4

"Fence posts"?

Reply to
Richard Henry

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