Ive been through a majority of the archived posts and did see one stating that the 1A2 interrupter has a hard wired ring cadence when used with common audible (CA). I have an installed and working WECO 551C with CA working with a 118 freq generator. Looking to mod the install to do 2 short rings on CO line incoming calls, either on some lines or all lines would be fine.

I know that old style Bell System exchanges (1960-1970s) had some switches that did 2 short rings to subscribers. I am wondering if there is either a practice or off-label mod to emululate this behaviour on 1A2.

Thanks in advance for reading my post.
-Alan

The incoming CO ring first activates the R relay in the line card. The R relay starts the interrupter motor by grounding the MS ("Motor Start") lead. The interrupter has cams and contacts that produce the "0ne second ON, three seconds OFF" cadence, that is fed to the CA lead on the line cards via the RN ("Ring iNterrupted") lead. There is an option block on each line card that allows the installer to provide (1) interrupted ring, (2) steady ring or (3) ground to the CA lead.

If the central office double ring you refer to is what the RBOC's call "distinctive ring" and you wish to pass this along via the interrupter circuit / CA leads, you are not going to be able to do that. The interrupter will give you 1 ON, 3 OFF regardless of what cadence, or cadence fragment, it detected to get it going in the first place.

If your installation is small enough (Is this your own set-up, being used as a "hobby" sort of thing?) then you can wire the ringer in each set, or provide EB-type line ringers, so that they follow the incoming CO ring directly. (You will need one ringer per CO line.)

If you are clever with electronics, you can produce a circuit board that will take steady generator and make psuedo-distinctive ring cadences, and send them out via the CA leads. You would use the output of this circuit instead of the RN output of the interrupter.

Very good, Arthur. Very clear and concise.

Thank you.

Sam

Years ago, I accomplished double rings by connecting a single pole slave relay that has its coil driven by the interrupter's "LF" output. The contacts on this relay would then switch the "RN" output. The LF and RN cadences were aligned so that it provided a perfect double ring. I just used this switched output to feed the appropriate line cards. It worked well.

A means to pass CO double rings to the stations was to strap the 400D cards for steady ring. There is no ring generator used in this scenario. The ring side of each CO line is strapped to the CA terminal for its associated card slot. The RG and RB terminals on the 551's 66 block then became the common audible output to the stations. In this case, the true ring cadence from the CO is passed straight through to the ringers. Of course, this was ringing to ground, so the CO must be a 'real' one in order for it to work. It also required that the ringing plant in the CO to be synchronized of all hell would break loose when multiple calls would arrive.

"Years ago, I accomplished double rings by connecting a single pole slave relay that has its coil driven by the interrupter's "LF" output. The contacts on this relay would then switch the "RN" output. The LF and RN cadences were aligned so that it provided a perfect double ring. I just used this switched output to feed the appropriate line cards."

Just when I get cocky and tell myself that I know everything about 1A2, somebody deflates me, you clever rascal, you. I am going out to the barn tomorrow and try this modification on one of my shoeboxes! Where were you when I needed you about thirty years ago?

Trust me, Arthur. I'd be happy if I knew half of what you've forgotten.

I stumbled upon this quite by accident when I dismantled some 6A intercom equipment and was trying to put it back together in 1978. I was trying to devise a way for intercom calls to ring double while maintaining single rings for CO calls. About the only thing that I was ever able to accomplish was the double rings.

This place never ceases to amaze me!!

Thanks for everyone's replies. Here's a bit more info based on your replies...

- Yes, this is a hobby system in service at my residence.

- I mentioned the distinctive ring CO cadence only beacuse we had that when I was a kid in the 1970's. I do have 2 POTS CO lines today, but its a different exchange, and the CO only provides a single ring. (In fact when I had the 2 lines turned up in 1997, I inquired about distinctive ring on line 2, but the Verizon CS rep thought I had 2 heads.) I know the CO switch can do it because Verizon had an optional service where you could have 2nd phone number for one line, and the 2nd phone number would ring down with 2 short rings. (Of course the Verizon CS rep had no protocol to order this unless I purchased a 2nd phone number).

- I like Arthur's suggestion to circuit the 118 output and make my own cadence. I'm thinking of relay with a delayed coil latching time.

- I like Ed's suggestion to drop in a single pole relay on the "LF" output. Sweet!

- Another option is to use the CO candence for line 1 (with a non-CA ringer), and use the CA cadence on line 2. While this is not really 2 short rings on line 2, its a faster cadence than line 1.

Thanks,
-Alan

Just a thought... Since the cadence for CA comes from the interrupter why not pick up a spare one and see if you can have someone machine you a new cam for it or modify it?

Because doing so would mean that only the modified cadence would be available. By having a slave relay to switch it, the original cadence is there for normal uses and the derived cadence can be used as needed.

Ed said: ...connecting a single pole slave relay that has its coil driven by the interrupter's "LF" output. The contacts on this relay would then switch the "RN" output. The LF and RN cadences were aligned so that it provided a perfect double ring. I just used this switched output to feed the appropriate line cards. It worked well.

I would assume I would need to pull the 551C KSU off the wall to access the backplane to wire as you suggested to the "LF" output?

As a temporary measure, I punched down the coil of the relay to "LG-L" for line 2 on the system 66-block, and put the relay contacts in series with the 118 ring generator. Works very nice, thank you. This scheme of course doesnt use CA for line 1 at all.

There is an LF terminal on the lower right side of the KSU's internal 66 block.

This is very interesting to me. I was in sales for Bell in early 1970 and sold one of the first ComKey 718 systems anywhere. No modifications were supposed to be allowed, but it didn't take long before they were made anyway. The same customer who bought the 718 upgraded to one of the first 1434's a few months later. As I recall, this was the first key system with optional music on hold and it sold like flapjacks.