atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1a2 system

Hi. I used to have a working 1a2 telephone system. I have a bell "shoebox" ksu with power supply, and 4 line cards. I also have a melco mc-9 Combination intercom. I will post pictures of the intercom, but assuming i hook the system back up with 4 2564 telephones, how would i hook up the mc-9 ?? Thanks.

I can help you with this, but there's a lot to it. The first thing I will need to know is that brand of "shoebox" KSU you have; is it a Western Electric 551A, B, C or it is it an ITT 601A. Just in case you have trouble locating the information, here are some pointers:

551A is light gray, has a hinged cover which swings to the right and has a twist-lock power cord on the bottom right corner.

551B is very similar, but the twist-lock AC power connector is eliminated and just a plastic grommet is in the hole for the power cord to pass.

551C has a dark gray lift-off cover and very little visible wiring inside the unit. All wiring is behind the backplane.

The 601A has a white lift-off cover with an ITT logo at the bottom. All card slots are horizontal and are on the left side of the chassis.

While we are at it, check inside the phones for buzzers. If they are AT&T/Western Electric sets, chances are that they are there. If ITT or Comdial, the only way to know for sure is open up the sets and look. The buzzers should be connected to the yellow-orange or yellow-green pair, but actually any spare pair can be used.

Once we have this information, I can help you plenty with this. I will be out of town this weekend, but will be happy to help you early next week.

[This message has been edited by ev607797 (edited May 13, 2005).]

Dam ev is old

Easy there SS! I am only 43 and I started working on 1A2 when I was 14! Too bad I didn't pay attention in high school to the important stuff I would actually need to know in life!

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Ed
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How come there's always enough time to go back and fix it a second time?

The melco for intercom will work on the power
supply 18-to 24v dc this is a talk crkt. There is not much to it. It's called basic telephone man stuff. The thing is just a tone relay providing a contact. It dosn't matter what western elect. type unit is is

If you want to run your buzzers then use the B battery....of the power supply. A combo of the both can work on any western electric power supply, as we are working on a rt type 1900 type intercoms.... I can't wait for my next service call. Besides i can make it a 19
zone unit with paging if you like.

I just re-installed a 1A2 system in my home. The Melco C-19 or any 1A2 intercom system in fun to work with, I have mine turn off/on outside lights, access an outside line & even access the answering system. The circuitry I made is really quite basic. It's nice to hear 1A2 still exists other than my house. My concern is of course, parts. My biggest concern is finding a new interrupter if mine ever fails. But..on this forum I've learned there's still a few suppliers out there stocking 1A2 parts. Then of course there'e E-Bay. I don't have a schematic for the "Shoebox" KSU but do for another model with 6 line card slots.

contact me off board with interupter mdl. i have a bunch of old equiptment around. 1a2 even using the sanbar units were extremely hearty.

I'll try to find the model number. It's a small interrupter, I've seen larger units in the larger line KSUs. I can remeber someone making a solid state replacement interrupter. I'll let you know if I can find the model number, thanks.

Here's what I can tell you to get you started. All shoebox KSU's have power terminals in the same general vicinity on the lower right side of the 66 block. You will be using AG and AB for the "talk" battery and BG and BB for the "control" battery. The intercom unit should have terminals labeled the same way.

Where it gets tricky is the signaling. You will need to check your buzzers in the phones to determine what voltage they are (blue wires on the buzzer indicate 10 volt; red wires indicate 18 volt). Once you have figured out their voltage, figure out which pair in the line cord they are connected to (usually yellow-orange or yellow-green). Connect the yellow wire of this pair from each station to the LG terminal on the KSU block. Connect each of the orange or green wires to a separate "R0 through R9" output terminal on the intercom block. Connect a single wire from the "AUD SUP" or "SB" terminal on the intercom block to the KSU's terminal LB if using 10 volt buzzers or SB if using 18 volt buzzers.

Next, assuming you will be using line key #5 on the phones for intercom, connect the black-green pair from all stations to the T and R terminals on the intercom.

Lastly, you will need to connect the lamps. Connect the black-slate lead from all stations to terminal LG in the KSU. Connect all slate-black leads from the stations to the intercom's "L" terminal. Connect a single wire from the intercom's "LB" terminal to the KSU's "LB" terminal.

My memory is a bit rusty on the intercom's terminal designations, so if any of the ones I have mentioned isn't there, just let me know and I will assist you further.

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Ed
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How come there's always enough time to go back and fix it a second time?