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

The yellow slate was connected to B1/R1 leads from the CO line card out of the KSU . EV do you remember working on diode matrix problems with an office full of 20 button sets ? What a nightmare sometimes .

How about setting up multiple button&buzzer keys on a 20/30 button set .You could spend all day just modifying 10 sets .

Twisted:

Yes, if you wanted a single CO line to ring on a 1A2 station, they you could wire that line directly to the yellow-slate pair of the station cable. But, if you wanted multiple lines to ring at the same set, you had to use the internally-generated ring cycle and voltage. This is because if you tied multiple CO lines to the same ringer, they would be effectively tied together.

Internal ringing also created the flexibility to have various combinations of lines ringing at different stations by using a diode matrix to isolate common ringing for some stations. For example, three lawyers all had their own two lines that rang at their station, but their common receptionist had all six lines set up to ring on that station.

Oh, yes OBTW. I remember many sites like you mentioned. We used to service the Kennedy Center in Washington DC that had hundreds of lines, even more stations and lots of mixed ringing. They had lines coming from cards in multiple closets backfed over house cable, lamp extenders, you name it.

It really got fun when there were transfer keys involved. As if the matrix wasn't already confusing enough!

Yes I worked on the 1a2 at RCA records buildging in Hollywood in the mid 70's. The entire building was 6btn to 30btn keysets . The floor that the lawery's were on was the worst . We would draw names to see who would take the service call or move the phones around . Finally it was just mine and one other tech names in the hat .

You mentioned a transfer key Ed. This was possible on the 1A2 system? Could you actually intercom (dial) directly to another extension? From what I have been reading, you installed buzzers in the phones for intercom but was it private 2-way?

Sure, there were multi-path intercom systems available. The AT&T/Western Electric 6A intercom was huge (as in size; all 23" rack-mounted relays that got bigger by the number of stations) but it still only had two paths. The first was a common path shared by everyone, but once a call was dialed, the parties were shifted to a second private path. Once the private path was in use, the next intercom call was on the public path. A third call attempt became a party line.

This was also when people actually got up from their desks every once in a while as opposed to today! If the intercom paths were busy, people just got up and went to the person they were trying to call!

AT&T/Western Electric came out with an advanced intercom system that was similar to a small PBX that was called "Dialog". It had many talk paths and functioned much like a PBX with built-in lamp flash rates for the 1A2 sets, etc. It even had clear plastic overlays for the faceplates on the phones to provide feature dialing codes. It was pretty sophisticated for it's time. Maybe that's why it didn't last very long.

Tone Commander also came out with the Multi-link intercom system for 1A2 called the ML-8000. With the proper cards, I seem to recall that it could go up to 8 talk paths. It also functioned much like a PBX. All intercom call paths were private. Ringback and busy tones were provided when making calls (this was an option). Once the equipped path capacity was reached, the next call attempt resulted in a busy signal when going off-hook. These things were VERY popular in the DC area through the 1980's.

Both of these systems provided "real" ringing or signaling (repeated) as opposed to the single buzz with earlier intercom systems.

Melco and Valcom had multi-path systems as well, although not quite as sophisticated.

Transfer keys were more for ringing on CO lines. Say for example an executive was going out to lunch, he could turn on his transfer key (a side car toggle switch) and his private line would then ring at the receptionist.

EV, This is a little off subject but did you ever work on the Tele Resources 32 "PBX" ? It came out in the mid 70's and was discontinued by 1981 .

Nope. Never touched PBX's until Mitel SX100/200 in the mid 1980's. All I ever worked on was 1A2, Comkey and electronic key until digital hybrids became the norm.

The analog sx100/200 Mitel's were a rock solid pbx as long as you had enough dtmf receivers and the power supplies did not over heat . I started on the NEC Crossbar 60/120 pbx's .

I still have sx-100 & 200's out there on Nantucket