atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Can anyone tell me why...

Matt, I don't know how well this is going to work without breadboarding it, but. An electrolytic capacitor from gate lead to source lead will slow both turn on and turn off. Value? Start with 10 uf and work your way up. Any voltage from 16 volts on up for voltage rating. The uf value will change the lag for turn on and turn off. Something from 1uf to 100uf. I'd suggest using alligator test leads to expirement. Makes it easier to change capacitors. Positive capacitor lead to gate lead, negative capacitor lead to source lead. It's a mosfet transistor, so even 1uf may be enough. Increasing the uf will increase lag, decreasing the uf will decrease lag. John C.

If the previous method doesnt work, putting the same value(s) across the relay coil will have the same effect, although it may require a whole lot more uf. Again, 16 volts or better for voltage rating. Negative lead to drain, Positive lead to positive 12 volts. FYI, putting + capacitor leads together and - capacitor leads together, causes the uf to add, i. e. 12uf and 22uf = 34uf. John C.

I think the lag on turn off is going to cause a false hold condition. Wish I had a 1A2 set up to play with. Put a buttset, turned on, on the 400 card output for line 1, white blue pair, temporarily short the A control white orange pair to light the lamp. Then remove the short across the white orange pair and I'll bet the line card will go on a false hold. Opening A lead before the talk pair is opened does that. Turning the lamp on slightly before or after T and R close, is insignificant in the real world. But, when you hang up the phone, the A lead has to open first, or within a few microseconds of T and R opening. John C.

Remote Hold as Arthur stated was the great nightmare. God help you if you found that job in your bin in the morning. Management would always give you a reasonable amount of time to do the job.....say 2 hours. It usually wouldn't take you more then....... say 2 weeks. And then it wouldn't always work. Or it might work - for two days and then stop working and then start working again.

As Arthur said: ARRGH!

The job is this-

A customer has two offices across town from each other. He wants the same lines installed on key sets in both buildings. When a call rings in, both keysets ring. That's easy. When a line is picked up in Building A it should go steady in Building B (too). When it's put on hold in Building B it should wink in both places. etc.

This was handled with a half pair per line run between the buildings that was tied to a collection of relays (6B, 17B, 18D) wired in arcane fashion. To fully guarantee productivity a pure white goat was then sacrificed and the blood poured over the ....

Well, not really, but you get the idea.

It was A lead control raised to the "Nth power" It was a nightmare.

Later Sanbar came out with a card that took a full pair between sites and replaced the 400 card at each end. I never used them and don't know if they worked.

A nightmare.

Sam

The Teltone 487 solved the whole problem. It is a very complex circuit (physically it fills all the available volume that a 400-type ktu takes up in a shelf.) It weighs a lot. It has many dip pswitches for setting up all the variables. And best of all, it requires NO extra pairs between DPA's.

I have a couple of them, and I plan to hook them up in my museum which will feature a step-by-step PBX and a lot of 1A, 1A1, and 1A2.

Thanks John - I'll run up to rat shack tomorrow and start the experiment. Doesn't really matter if it works or not, causes false hold, or bursts into flames. Just another thing to play with, I really appreciate the tips. Will let ya know.

Sam - I can't even begin to imagine. These must have been some high $ companies to want, pay for, and even think they really need that sort of thing. I mean.... I can see it being somewhat useful, but jeezy weezy. I wonder how many times it broke because someone else came along and cut and used the line for something else. Also can't even begin to imagine troubleshooting when it broke.

Would have loved to be around for that ride though.

John -

Looks like something across the MOSFET is gonna be the way to go. I found a 100 uf, put it on the mosfet, waited 4 mins... nothin. So, something smaller there.

I had a couple 1000uf's as well, first put 1000uf and then 2000 uf across the relay, no apparent effect, switched right on.

Will let ya know more tomorrow.

...later...

10uf causes engagement after about 15 secs. Gonna have to go lower still..

Thx
Matt

Matt -

I don't know what the tariffs were, but I don't think it was hysterically expensive. The bigger companies usually had PBXs, not key systems. We did some pretty fancy stuff with PBXs, networking them, bouncing calls back and forth, etc.- but that was easy compared with Remote Hold.

Sam

Arthur -

Do you have any specs on that 487? I never heard of it. I'm not talking a schematic - just a circuit description.

TIA,

Sam

Jeez I'm an idiot. Ed already said... "The A leads must close before T&R when going off hook". Adding a delay to the A lead closure isn't going to help. Sometimes I wonder what's wrong with me.

I think I like to tinker too much.

I guess what I really need is a -2 uf cap.

I guess it's off to sandman one day. For now I kinda like having line 3 light up if someone is using an SLT.