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International ring cadence: special interrupters?
#631853 08/14/19 07:52 PM
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I'm curious if 1A2 was used in countries that had different ring cadences, like the double-ring popular in Europe and such, and if so, were there special interrupters in the KSUs to regenerate that same cadence?

Since 1a2 regenerates central office ringing with the interrupter's gears+micro switches, just wondering if there were special variants of the interrupters for Europe. Or perhaps one could change out a few gears in the stock interrupters for doing special ringing, like the double-ring thing (400 ms on, 200 ms off, 400 ms on, 2000 ms off).

One of the folks who purchased a few of my "single board KSU"s is located in a country where the CO supplies the double-ring. I was going to supply a software mod that handles fixed ringing, but was going to use the north american single ring cadence (2/4, or I actually found 1/3 to be more to my taste), but wasn't sure if 1A2 supported other kinds of rings.

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Re: International ring cadence: special interrupters?
Greg Ercolano #631856 08/14/19 09:36 PM
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Check out this map.

Seems like the wiring would be the same but the Line Cards would be different. I know Redbul has posted it here let me find the link..

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Here is the thread I remember reading: https://sundance-communications.com/forum/ubbthreads.php/topics/624157/1
the third post down:
"...Europe uses 25 Hz ringer instead of 30 Hz in the US (half of power net frequency). But ringer voltage in the US is higher 90-110 V vs 60-75 V in Europe. This is not enough to give ringer the full amplitude. But some wood may resolve this issue: couple of matches to position the ringer coils perfectly on the metal core and it starts ringing on lower voltage. I want one day to put a KSU as well with the ringer generator for audible signalling. Then difference in voltage will not be a problem at all."

So perhaps the Power Supply and/or the Line Cards

Last edited by Professor Shadow; 08/14/19 09:45 PM. Reason: Remove from HOLD

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Re: International ring cadence: special interrupters?
Greg Ercolano #631858 08/14/19 10:22 PM
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You might find something on this site.

or here.


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Re: International ring cadence: special interrupters?
Greg Ercolano #631860 08/14/19 10:35 PM
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Oh, I didn't mean the ring AC frequency.. I was referring to the "ring sequence" output of the interrupter which switches the ring power on and off for the ring pattern. Pulling up a KSU diagram, it's this bit:

[Linked Image from seriss.com]

In the US the ring sequence is: 2-sec-ring <4-sec-pause> 2-sec-ring ..etc..
in the EU the ring sequence is: 1/2-sec-ring <1/4-sec-pause> 1/2-sec-ring <2 sec pause>..etc..

Pretty sure the pattern of ringing is controlled by a gear in the interrupter.

I was wondering if this is something 1a2 had options for, or if it just gave the US pattern for business phones and that was it.

Re: International ring cadence: special interrupters?
Greg Ercolano #631870 08/15/19 02:29 AM
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1A2 was generally NOT used in Europe - except in American Embassies where it was all over the place. To my knowledge no European phone companies used it. I saw a German company's (TN) multi line equipment once and it was much larger than 1A2. In England the cop show Cagney & Lacey was - for some inexplicable reason - immensely popular. The gals had 1A2 phones on their desks and for a while everyone in the UK wanted one, to no avail. The 3 -line phones that had a separate hold button for each line could be modified to work across the pond, but for the most part, that was it.

GTE sold some PBXs and COs overseas, but not 1A2/10A2.

I had a friend who had been the chief CO engineer in British Guiana who (in the 60's or '70s) installed 1A1 equipment and phones for an American airline down there, but that was a special order.

We had the option on many digital PBXs to offer Ring Tone European (RTE) or Ring Tone American (RTA). Before Caller ID many firms selected one ringing type for DID calls and the other for Internal calls. It made it easier for people to know how to answer the phone ("XYZ Corporation, Accounting Department" or "Bob here"). But on 1A2 it wasn't an option. At least not one I ever heard about.


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Re: International ring cadence: special interrupters?
Greg Ercolano #631874 08/15/19 03:38 AM
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Thanks Sam, yeah, I was thinking maybe 1A2 was just States-side only, as the EU had their own phone companies + manufacturing.

Yeah, 1A2 phones ended up in just about every 70's cop show.. Mannix, Cannon, Charlies Angels.. they usually
got all that stuff right. There was always a business office situation; anyone with a secretary had 1a2.

Phones were often a big part of film/tv to move the story along. It's hard to think of a cop show without at least one
sequence where a phone was used. It was always fun to see if the business phone lamps correctly, and if people operated
the calls correctly. "Lemme put you on hold.." and then hits another line button with Hold in between.. oops, lost that call!

Re: International ring cadence: special interrupters?
Greg Ercolano #631891 08/15/19 08:25 PM
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Im nowhere close to being a genius, it took me 2 years to figure out a button/buzzer setup. But I always thought an interrupter worked like this.Calls come in from CO starts interrupter motor which in turn operates separate contacts which in then applies voltage from power supply for ringing, lamp flash, etc.Seems like the incoming cadence wouldnt matter.Doesnt address co voltage though.Am I totally wrong.

Re: International ring cadence: special interrupters?
Greg Ercolano #631898 08/15/19 09:31 PM
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1a2 definitely regenerates the ring cadence, power, everything. It has to because the CO's signals can't be mixed, there's only one bell in each phone. And when two or more lines are ringing at the same time, they can be out of sync with each other, creating really annoying ring patterns that can sound bad.

So 1a2 completely regenerates ringing; the interrupter for the cadence, and the line cards determine which line is ringing, and the optional diode (see above diagram) can control which specific extensions ring.

The line cards in the 1a2 phones have a ring relay each, and the output of the relays all common back together for the 1a2 Y-S pair in the KSU wiring.

So ringing really is a separate circuit of its own; ring gen -> interrupter -> line card ring relay -> phone -> ring gen ground. There may be other switching in there for more complicated setups, but I think that's all there is.

Diodes are added to the phone extensions to let you program which phones ring and which don't, e.g. so that one phone can ring for calls on all lines, and another can only ring on one particular line, etc. The diodes prevent ring voltages from sneaking backwards to ring unwanted phones, but they also chop off half the AC wave (rectifying it). But 1a2 bells are polarity sensitive, and only ring on one side of the AC wave, something I proved to myself on the bench by applying DC in forward vs. reverse orientation; the bell clapper only moved when positive voltage was applied to the red wire, and ground to black. Switch them, and the clapper didn't move at all. This is apparently why ringing sounds the same with or without diodes. Had the bells been responsive to both sides of the AC wave, the bells would sound different and weaker with diodes, but not the case with polarity sensitive bells.

Last edited by Greg Ercolano; 08/15/19 09:33 PM. Reason: Added bit about regenerating ringing.
Re: International ring cadence: special interrupters?
Greg Ercolano #631901 08/15/19 10:14 PM
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@gelehu: Oh, and yes, incoming cadence shouldn't matter to trigger 1a2 ringing. But what people would expect to hear from the the regenerated ringing on the 1a2 phones in an EU environment would probably be their local telco's ring cadence they're already used to, i.e. that double-ring thing as an example.

So I was wondering if 1a2 had such an option, but sounds like not, if 1a2 was a US thing only. I'm sure one "could" fit the interrupter with a different pattern of notches for the rotating gear that handles ringing, but it sounds like that wouldn't have been an option if 1a2 wasn't deployed world wide. Apparently different countries used entirely different equipment, with the few exceptions Sam noted (embassies).

Certainly EU phones I saw while traveling in the 70's and 80's didn't look anything like the Henry Dreyfuss design (model 500) that became the default in the US from the early 1950's onward.

Re: International ring cadence: special interrupters?
Greg Ercolano #631904 08/16/19 12:04 AM
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Originally Posted by Greg Ercolano
@gelehu: I'm sure one "could" fit the interrupter with a different pattern of notches for the rotating gear that handles ringing,


Those would be cam wheels. There is one for lamp flash, one for lamp wink and of course one for ringing. Each cam wheel has a (sort of microswitch) switch that has an arm with a roller that follows the contour of cam. When the motor starts all cam wheels, being on the same shaft, rotate which causes the switches to turn on and off in step with indentations on their respective cam wheel. The speed of the motor and the spacing of the indentations on the cam wheels are what determine the lamp flash, wink and ringing patterns. Simple enough.

Now, if you wanted to generate a European cadence, all you would have to do is make a new ringing cam wheel with indentations that would generate that ring pattern. That assumes you could get the interrupter apart to replace it.

And of course this is very old school. With electronics this could be done very easily. I vaguely remember somebody who actually made and sold a solid-state interrupter replacement? Maybe this could be your next project- with a switch on top of it to select US or European ring cadence. cool

-Hal



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