sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1A2 power supply with backup?

Fellow techies,

I'm curious as to whether anyone ever made a 1A2 system power supply with built-in battery backup?

This is really pure curiosity. I have a perfectly good AC-based UPS for my own system.

Thanks much.

None that I know of. Remember that the limited electronics in 1A2 were quite tolerant to voltage surges, plus all that they provided were features. Even without power, you could still make calls and with power failure transfer wiring, you could even receive them.

Back in those days, there was no voice mail, e-mail, cell phone or even any sense of urgency as there is today. It was perfectly understandable to leave a written message for someone, or for the more high-tech offices, leave a message on their answering machine.

For the really important people, like the town doctor, they used an answering service. The answering service's PBX usually had a bank of batteries for backup.

Refer to BSP 167-449-101 "47C POWER UNIT"

Identification, Installation, and Connections, Issue 1, 1971.

(parts quoted)

1.01 The 47C power unit...is intended to provide emergency power for Key Telephone Service installations during commercial power failures. The power provided to the Key Telephone Service installations is used for switching circuits, lamps, and an interrupter.

...

1.03 The 47C power unit is arranged for plug-in addition of the KS-20390 L1 battery which must be ordered separately.

...

Table A (outputs)

-20 V DC Signal
-20 V DC Talk
10 V AC Lamp
10 V AC Lamp
FREQ GEN

...

(end quote)

I can photocopy and fax the BSP if you want to see the whole thing.

Additionally, please remember that even without any power back-up, the interrupter in 1A1 and 1A2 installations has a "homing" contact, similar in application to the one in your car's windshield wiper motor, that ensures that the lamp flash and common bell contacts always land in the closed position.

In the event of the opening of a 10Vac interrupter fuse, or the failure of the interrupter motor, an incoming call will still be signaled, albeit with a steady ring and steady line lamp. In the event of a complete power failure, if the subscriber has line ringers, power failure transfer relays, or a central-office supplied generator feed, the calls will still be signaled audibly.

I installed one back in the very early 70s. It was a standard 1A2 system (I believe it was a Stromberg Carlson, but it might have been AE or even ITT - I really don't remember) But it had a different interruptor and a special Power Supply. The only taps were DC - A Battery & B Battery, though there may have been multiple B Battery taps. There were 2, 12V batteries wired in series that provided backup power. We put 52A lamps in the sets which ran on 24V, and the small square metal buzzers that were 24 VDC and line bells for ringing. The 400 cards and the Intercom (207C with a 216) of course used 24VDC.

This may have been the 5th 1A2 system I worked on. I assumed this was a standard optional package and thought nothing of it, so I didn't pay a lot of attention to the job.

It turned out to be the only one I ever saw.


Sam

Sam, WE also made an interrupter that used DC, for installations that only had a DC supply available.

Even into the 1970's, there were a few buildings in Manhattan that only had a DC supply, and most electronics of the time would not work, unless the apartment dweller or business owner had an inverter, or a rotary converter.

One such was the Hotel des Artistes at 1 West 67th Street that converted to AC in the late 1970's.

NYTelCo had a -48 Vdc feed and a -24 Vdc feed over subscriber pairs to the basement feeder, to power the cordboard and the key systems in the building. The CO is on West 73rd Street, just 6 blocks away, so the supplies did not suffer too much voltage loss.

Too rich for my budget

I know the building (and the CO) very well. There was a restaurant "Cafe des Artistes"on the first floor that had beautiful murals (and pretty good food!).

During the blackouts in the City you could easily pick out the DC buildings - they still had power!

My friends building on University Place had DC power for the elevators. During the blackout we discovered that the sconces in the hallways were powered off the same source!

I wish I had paid more attention to the installation. If I had known it was the only one I'd ever see......


Sam

It's fascinating to me that a question about obscure and obsolete phone stuff can turn into a discussion about architecture and the history of electrical transmission.

That's why I like going to this section. I do wonder if I can still get K51A or 10ESB lamps for my home 1A2 system somewhere. I do have one of those red LED 5 line sets, the rest are lamps.

Just put 51a lamp in google.