atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems How many ringers?

I just picked up an ITT 501 KSU with a dial intercom and a bunch of odds and ends from a friend and when I printed and read the practice it stated a maximum of three electro-mechanical ringers may be connected at the same time. This seems awfully paltry for a 6 line KSU. This got me to thinking, how many ringers can be connected to the 118A generator in my shoebox? And what will cook first if there are too many? The generator? The interrupter contacts? I currently have 9 sets connected to the shoebox and it seems to work just fine. I know at some point there's a limit, but I've never seen anything mentioned here about limits on ringers, though. And one last question, could I use a 118A generator in the ITT KSU and just forget about the built in ring supply to ring more sets? This is all assuming using CMB for all lines on all sets. I will admit this may be all conjecture, I'm not sure I want to replace my baby with an imposter.

Are you certain that what you read referred to the KSU / interrupter, *OR* did it refer to the signalling contacts inside the intercom unit?

Three ringers is not the correct total for any CO line ringing situation that I can imagine.

Maybe a misprint?

Arthur, that was the practice for the ITT 501 built in ring generator. Not wired for CO powered ring, but local supply for common bell.

Let me see if I can find it and quote it...

My mistake, that reference was in the section covering the 512A KSU. The thing that concerns me though is, that was a much bigger KSU and the practice reads "The system power supply is capable of ringing four electro-mechanical ringers at one time. Hence, no line should be arranged to ring at more than three telephones."

Pretty lame. I will do some research and see how much current a C4A ringer draws. The generator supply for a 584C panel, e/w a KS-15900 interrupter, is fused at 0.5 amp.

I do know, however, that just from a physical size comparison, many ITT frequency generators are much smaller than the WE / Lorraine ones that are inside the typical 20- and 30-type (or equivalent) power units.

I agree. That's pretty weak for a system of that size/capacity. How about the 118A in a shoebox? I'll bet I'd fry the interrupter contacts before that boat anchor of a generator gave up the ghost. (just speculation, because I really don't want to fry either of them)

The 501 that's on its way has a Lorrain P/S, but I have no specifics on it. I just looked at the S/C clone of the 501 on ebay and its P/S gives a rating of 110V @30HZ at .05 amperes. That seems pretty weak for a 6 line KSU that is made for 9-18 stations.

The interrupter contacts can switch 50 lamps total. Each 51A lamp draws a maximum of 0.045 amp. 50 x .045 = 2.25 amps.

So, the limitation is not on the interrupter contact, but on the ringing supply itself.

TAD (tomorrow's another day)

I think I saw a similar limit in the BSPs (or other practices), and had the same "Huh?" reaction as Chris. Seems like a contradiction; something like a 584 panel ringing more than two phones at once doesn't seem like a rare occurrence. It did always strike me as odd that a lot of PBXs and KSU supplies have a small ring generator supply; why not bump the output to 100mA?

Fun fact: Lorain Products Corp is based out of Lorain OH, right near Lake Erie, and about 15 minutes from where I grew up. They got bought out at some point and are currently part of Emerson Network Power. I should really look into buying one of their power supplies at some point...

It doesn't seem to make a lot of sense. If the system is wired for CMB, then anytime the line rings all the phones would ring. I have 9, that's right, NINE sets on my shoebox, and they ring just fine. I have to think that in such short bursts, it can't be that hard on the frequency generator. 9 sets all wired for CMB is quite a sound when someone calls.