atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 551B KSU Ringing Issue

How did grounding the KSU fix the intermittent no-hold problem?

I was just axin myself the same question, Arthur. I will agree that the early 400H cards had a mind of their own, but I never heard of the absence of a chassis ground causing a hold issue. The 400H, Issue 2 series seemed to overcome just about all of the glitches, shortly before they were sent out to pasture.

Nah, that was the WECO 400H, Issue 1. Those things were completely unpredictable. I don't see any of them in the OP's pictures though.

400E was of ITT manufacture and they were bullet proof. Bell even started using them in Washington, DC instead of WE400H ones due to the huge amount of federal government 1A2 at the time. They got tired of chasing their tails.

Up here in Seinfeld Country, we were issued SanBar 4000F cards made in Mexico. They, too, were bulletproof, and even had that innovative red LED to indicate busy. That saved time and labor over the old method of identifying one 400D card in a Parker rack of 130 slots -- that is, by asking the subscriber to flash the SWHK until we could determine which KTU was clicking.

There was a Western Electric 400E line card. An article entitled"Advances in the 1A2 Key Telephone System", in the October 1970 Bell Laboratories Record, has a photo of the Western Electric 400D and the Western Electric 400E side by side.They had reduced the number of components from 41 to 17. This was done by replacing the transistors and all the components on the small secondary circuit board with an integrated circuit chip. It must not have worked out because in the early 70's the BSP for the 400 series noted the 400E Manufacture Discontinued.

Very true about the WE400E. That one came and went in no time, in fact I'm not sure if they ever went out into full distribution.

Arthur, C&P Telephone here was also using Brand/Rex (Teltronics) LC-400E cards and they got a lot of attention. The circuit boards were blue, the handle was white and the manufacturer's label was quite an eye catcher. They were the functional equivalent of ITT's 400E, but they were better-looking.

I have a couple of the LC-400 cars, New in the Box.

I have no idea where I got them from. None.

Did they do anything special?

I'll have to look.

Sam

Not that I recall, Sam. They were just another player in the equipment game pre-divestiture when RBOCs could buy their hardware from sources other than Western Electric (ATTIS) and save some money.

Thanks, Ed. If I remember (a BIG if), next time I see them/think of them I'll look them over.

Sam

"How did grounding the KSU fix the intermittent no-hold problem?" he asked, not expecting to get a reply.