atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1a2 line detection, a-lead control?

Wasn't there a topic somewhere that someone wanted their 1a2 system to detect when a co line was in use? I would like to do the same thing. There's an old inter-tel system connected to the same CO lines in my home as the 1a2 system. What I would like to do is cause the line lamp to come on whenever the line voltage drops, wasn't there a circuit already meant for this? Otherwise it would be necessary to hook up some relays, or can this be done with the line cards themself?

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If you are looking for something that will indicate when the line voltage drops as in monitoring line voltage, then that's a whole different can of worms from the previous posts. If you want to just have something that provides a light when the line goes open momentarily to drop the line from holding, then I can help you. If you will send us your more detailed requirements, I know we can help you get it going.

What you want is an A lead control. We used to use them with an standard T/R answering machine to indicate when it was on the line. It's a little black box with a 4 conductor line cord on one side and a RJ-11 for the answering machine on the other. It senses current on the T/R and gives a contact closure for the A lead control.

Wire the wall jack with T/R from the 1A2 as usual on 3&4. Put A&A1 for that line on 2&5. Plug the A lead control into the jack and connect the CO line for your key system to the A lead control RJ-11 jack.

-Hal

We also have Melco A/A1 detectors, new in the box, that will monitor the loop for activity and provide a contact closure to light the lamp if that's what you are looking for. They are hard-wired, but we have plenty on the shelf and they are cheap.

OK I knew there was a posting on this! It seems like the A-lead detector just goes in series between the CO line and the line cards? This would work fine, and I guess it just involves some hard wiring and no modification to the system? Is one required for each CO line? I was actually looking at building a circuit comming off the relays inside the inter-tel and closing a relay on each A contact to ground to indicate the line is in use. The problem is that my mother is now living with me and always picks up the line when I am on the phone because I am using the electronic key system. I did make an interface board to go the other way, flowing line current causes the relay to close on an unused extension on the inter-tel. Just want the same to happen on the rotary key phones.

By the way did the guy in the posting listed above ever get his A-lead control installed? I don't feel so silly being the only one here asking for 1a2 advice!

You shouldn't feel silly being the "only" one asking for 1A2 advice. Quite frankly, I have been seeing a bit of a resurgence in 1A2 use. It seems that it's the only equipment that can hold up to heavy use and it can be easily repaired in the field.

Yes, the Melco units I mentioned do wire in series with the lines coming in the the electronic key system. There is an incoming T/R and an outgoing T/R toward the electronic system. The Melco unit I mentioned provides an A/A1 contact closure toward the 1A2 to light up the line button. These units get their 24 volt DC power from the 1A2.

There is going to be a little bit of trickery in getting them set up, but I will be happy to aid you in getting them connected. They involve a few screw-terminal connections, but after that's done, it's a bullet-proof installation. You can install ANY electronic key (or PBX) system behind them and they will work the same way. Yes, one unit will be required for each C.O. line, but like I said earlier, I have a bunch of them on the shelf and will let them go for a fraction of their original cost.

Just remember that this A/A1 only works TOWARD the 1A2, so if a 1A2 phone is in use on a line, it will NOT light the buttons on the electronic key unless your system allows for external A/A1 input. I know that some systems, specifically Vodavi's older ones were designed with a minimal amount of 1A2 functionality.

Probably be a lot less painful, Get Your Mom an Inter-Tel phone!

It's no problem, when the 1a2 lines are in use they cut off the inputs to the electronic key system, I have installed relays that open the CO lines going to the key system whenever power goes to the line lights. The only problem has been to decide whether to wire up 6 relays for the 1a2 system or try and get something ready made.

Like I said, I have plenty of Melco S-64-1's available that will do exactly what you want, just PM me and I will send you some and assist you in hooking them up. These things are made for exactly what you are trying to do, but you will have to wire one for each CO line.