atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 760 speaker

I haven't seen one since I was a teenager, but I seem to recall that there was a fairly large control unit for the 3A/B system It was in a gray enclosure about 9" square and about 6" deep that mounted on the wall near the station being served. It was about half the size of a 551 shoebox KSU. All of the cables originated in there; there was a field of dozens of screw terminals.

Ed -

You must be slipping. It's a type 55 (either A or B) control unit and it's not 9" square by 6". It's only 8" x 8 &7/32" x 4 & 11/32" deep.

I swear you're amazing.

The only external loudspeaker was the 760. I don't think there was an "A" or a "B". If you got a panel phone with the built in speakerphone it used a 762A speaker.

I had a 3B speakerphone for a while. When the 4A's started coming out there were a ton of them available.

Sam

Sam, I'm still laughing at that one. You are a funny guy.

Please tell me you actually measured one of those and it was not by memory

Jeff -

I haven't seen one in years.

But I did cheat.

I looked up the specs.

Ed's memory is amazing.


Sam

Thanks for the info. That brought up a couple other things though - I never knew there was a 3B speakerphone. How did it differ from the 3A? Was there ever a 4B speakerphone system?

The speakerphone, to the best of my knowledge was a "Type 3". The earlier models were 3A, the later were 3B. Whether this was the result of the change from 55A to 55B control units I don't know. A lot of products took incremental changes that did not effect most functionality. Speakerphones were one example of this. Another example was the 584 panel - the mainstay of large 1A2 work.

There was an "A" version (before my time) that I believe was wire wrapped instead of amphenol connected, though I won't swear to it. The "B" version offered three interruptor option possibilities (Master, slave and external lamp relay). The "C" version which lasted through the '60s, 70's and '80s did away with the "B" option for external lamp relays. But in 99.9% of the situations you could mix panels on the job and not even notice any differences.

I believe that was the reason for A&B nomenclature, If there was not a major difference and the components were, for the most part, interchangeable then you got a letter upgrade. A major change - like the one from the type 3 to the type 4 speakerphone got a "full" nomenclature upgrade.

BTW, I don't believe there was a 4B speakerphone, but I'm sure someone will chime in if there was.

And, just to be difficult, I believe the best speakerphone of the time was the Automatic Electric 880 which, unlike its Western Electric counterparts was full duplex.

Sam

Precision Components' version of the 4A was marketed as the 4B, but aside from the beige-colored connecting blocks, power transformer, etc., I never noticed a functional or electrical difference. I know that the parts were interchangeable between PCI and WECO because we did that all the time.

Was the 4A full duplex? Was the 4A actually a significant upgrade to the 3?

I do not believe the 4A was duplex. As far as an upgrade to the 3B - I thought it was more modern, smaller and didn't require the big 55B control unit, but otherwise.....As I recall, sound quality was about the same.

Sam