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

A college radio station that I worked at had a 711B SxS PBX, with several shelves of 1A2 behind it.

We ran the lamps, and 2 of the 3 interruptors off of the 24vdc battery plant (the third shelf had a 10v interruptor, as it was added later, and never got upgraded.)

We had both 24vdc and 48vdc for phones, emergency power via an inverter, emergency lighting, and other station signalling applications.

[ The idea is that we could lose commercial power, and the generator backup, and still remain on the air in the event of a natural disaster (this is the San Francisco Bay Area, so that means earthquake.) We were one of the only stations in the Bay Area that did not go off the air at all during the 1989 Loma Prieta quake. We also had a portable generator that could be connected to power the station emergency power grid, including the battery charger.

We had similar protection at the transmitter site (Generator + UPS + manual start generator), and we owned the outside plant between the sites, as well as to other sites on campus. ]

I learned 1A2 in the early 80's. I had just mastered the diode matrix when the Tie Econokey came out. It was a small blue box and you entered a bunch of 0's and 1's in programming. So much for all my training.

Ah for the good old days when the only questions you had to ask a customer was: what phones do you want to ring and what should we set the hold recall for.

When I started in '83, they had one site that was a "business incubation" center. Your rent included a common receptionist that also did secetrial services for each tenant.

Each tenant had 6-button 1A2 sets, and the receptionist had a 30 button set.

My boss didn't understand diode matrix ringing, so there were a dozen external ringers in the closet behind her, each wired to a different set of B1/R1's

Diode Matrix becomes a nightmare when you start adding in ring xfer switches that do not share the same IDF/MDF ! I think that's what happened to Ed's hair ! :toast:

Amen, DJ on that one.

The Kennedy Center for the Performing Arts in Washington, DC pretty much took most of my hairline. 38 separate closets, main frame room the size of a three-car garage (shared with ATT techs as a field office for them), all 1A2 and Tone Commander Centracom behind Centrex, 26 gauge house cable, 144 separate intercom systems, lamp extenders, you name it. Key equipment for a department with 30 phones was located in a closet across the building two floors up because there were slots available there! UGH.

You want to talk about ring transfer keys on a diode matrix? I believe that they invented this requirement there.

"No wonder I like 1940's B&W B Westerns and not American Idol !"

Have you ever seen/watched 'Rustler's Rhapsody'? If you remember 'B' westerns and 50's Saturday matinees, you'll enjoy it.LYAO
I had to learn 1A2 from a book, that I got handed when the company I was working for that had a Code-A-Phone franchise in KCMO decided to get into telephone systems. Astoundingly, I didn't blow a fuse until the 3rd system, an ITT512, as I recall. And at the same time I'm putting in TIE 308, 516, and 2040.
The biggest problem us techs that transitioned from 'electronics' to 'phones' had was adjusting to + ground! Every elctronic tech knows that ground is usually -. Unless you had a dual polarity power supply for op amps or something.

Where did the positive ground come from in the telephone industry anyway?

If you want me to take a guess on that one, there was some debate as to which direction current flowed from a battery back in the early days of electricity. Most thought that it was from positive to negative, but at some point, this thought was disproved. This happened long after the telephone and supporting systems were developed, so maybe they just went with their understanding of current flow at the time.

I would also think that it would be desired to have the tip of the switchboard plug to be grounded so that accidental contact by the operators wouldn't hurt them. If you look at vintage photos of corded switchboards, all patch cords are stored with the tips straight-up when not in use. It was a little more difficult for operators to accidentally contact the sleeve or ring terminals on the plug's shaft that carried high voltages, especially on toll (long-distance) circuits.

Personally, since telephones were a brand-new industry, I think that they just went with whatever they felt like in the beginning and learned along the way.

That makes sense. I wondered if it had something to do with those cord boards. I have often thought the design of the 1/4" (TRS) jack/plug to be strange. Normally you would want the ground to connect first. That's why they made pin #1 connect first on XLR connectors (but then again, they came years later). The other design flaw about TRS is that the tip shorts out to the sleeve and the ring upon insertion.

You made me think here, with the current direction theory. Even the car manufacturers did the positive ground thing, didn't they? They were just smart enough to change to neg ground at a later date.