atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems ITT 501C Intercom

Success! I have buzzers. One of my phones lights the hold button when it gets buzzed, the other doesn't I havn't decided if I like it or not yet.

One question - there is a slight hum on the intercom line; is this normal?

I really like the "ringing" you get on the receiver when buzzing another station.... very cool.

Thanks everyone -

Matt

Reading through other posts:

https://www.sundance-communications.com/cgi-bin/ultimatebb.cgi?/ubb/get_topic/f/13/t/000488/p/1.html

it sounds like maybe I'll need to put in a 1000uf electrolytic filtering capacitor; I suppose across AB and AG (I say I suppose because I'm wondering if it should actually go across Tip and Ring).

I think the hum is caused by the fact I'm using the AB for both AB and BB. When using my old intercom card, there was no hum, so I don't think there is necessarily anything wrong with the power supply.

I'm thinking of going up to radio shack tomorrow to look for such a cap. I'm guessing it will need to be 24v or the next higher value available.

Thoughts?

Thx
Matt

The cap shoud go across AB and AG. Across T and R you would 'filter' the audio out! Try for at least 35 Volts, 50 even better. You may be overloading the 'A' battery supply, be careful. ITT601 power supplies are not nearly as forgiving as as the big grey 1A2 power supplies from Elgin or whoever. That little regulator card is small in size AND capacity. John C. (Not Garand)

Matt -

On most KV sets the Y/G pair is wired to the hold lamp. Of course many sets don't have a lamp installed at that spot so not all of them will light <G>.

Some sets allowed the use of a "phantom" 6th button - a "All Buttons Up" Itercom. If all your keys were up you went off hook and got T/R off the Y/Blue pair and lamp off the Y/G pair. Buzzing on the Y/O. Stromberg Carlson sets came standard like this and some WE sets (but I think you had to also pull up one of the hook switch buttons to activate it on a WEco set)

I always used Y/O for buzzers(except on Northern Electric/Telecom Logic sets in which case it was Y/Brown.

Confused enough?


Glad everything works and that you've got Intercom.

You can also add ICM only phones using 2500 phones. Connect G/R to T/R and B/Y to the buzzing pairs, then open the B/Y inside the set and connect a buzzer.

Sam

Thanks Sam, John -

It's good to know I can make an intercom out of a 2500 - that will come in handy some day. ANd thanks for the cap info John.... !

Matt

Well, I put the cap in. (1000uf, 35v) I bought 2, cause I figured I'd get it wrong at least once. The first time I hooked + to AB, and - to AG. Cap started to get hot, unplug NOW.

Went for a walk, realized (duh) AB is - (for some reason I just can't get that straight in my mind). Put in a new cap, it's not overheating though there is still some buzz. Not as much, but some. I can live with it.

And thus the intercom chapter is closed.

Stay tuned for the next project: MOH.

THANKS EVERYONE.

- Matt

Matt -

Do you have one or two sources of -24VDC on that beast? If you have two hook one up for A and the other for B.

Also - lift all the wiring off the power supply -24v, then take a butt set and go a cross it. If it still hums coming out of the supply, then that's it. If it doesn't, start attaching the connections one at a time and see which one puts on the hum. Trace that back and see - might be a defective 400 card or......?

Also that ICM I sent out will work Tone or Rotary - so if you dig up some old sets, it'll still work.

Sam

Matt, if you are using a non-601 intercom, You may be just plain overloading the 601's power supply. That will cause hum and consider it a warning from the 601 power supply! John C. (Not Garand)

Sam -

Pretty sure there is just one 24v output. See my PM for PS specs.

I'm thinking I have a ground issue or something. AG is tied to the power supply grounding screw as per instructions, and basically every ground (AG, LG, etc) is really the same point now. I tried disconnecting all keysets (2) and swapped in a third one (an ITT) in favor of the 2 WE keysets - same buzz. Then I disconnected the lamp feeds to the intercom, and the 18v station signal input... same buzz. My next step will be to disconnect everything from AB and AG; possibly everything from the entire KSU, and see if I still have a buzz on AB/AG...... if not, then I'm guessing it's the intercom putting out the buzz, since it feeds tip and ring to the keysets.

It's really not that much of an annoyance...... but it would be nice if it were completely silent.

I do have an ITT rotary, so it's great to know it will work with both!

Thanks Much!

Matt

Thanks John - I really hope that's not it.... as you can see from this thread, there has been a great gnashing of teeth any many, many attempts to get my old intercom card working. If I have to resort to finding a working intercom card for this unit.... I will be:

The one Sam sent me is very cool.