Greetings!

I'm an EE major who just entered the 1A2 world. (Bought my first WE 2830 set a few days ago). I had a few hardware related questions that I couldn't seem to find answers to in the BSPs I read, although it's entirely possible that I glanced over something. This forum has wealth of knowledge, so I thought I'd ask here. I'm eventually hoping to set up a small 1A2 system to connect to my Panasonic KX-TD1232 PBX. (This will be a local, non-POTS connected system in my apartment.)

1) With respect to signal voltage levels, are there any special requirements for interfacing a KSU to a modern PBX?

2) Generally speaking, how many phones can be supported by a single KSU, such as the 551C? (Not sure if there is a BSP that covers this.)

3) Is there a BSP that describes the intercom operation/usage?


I'm still in the process of tracking down a KSU and the associated RJ-21/Amphenol cabling. If by chance anyone is looking to offload a KSU (functional or not) or some RJ21 odds and ends, feel free to shoot me a PM.

Thanks!

Nick -

Welcome to the wonderful world of 1A2!

1- I guess it would depend on the individual PBX. I am unfamiliar with the Panasonic KX-TD1232 but basically the big questions to ask are: what voltage does it supply for analog extensions? Anything from 24 to 48VDC ought to work well. Then there's ringing current. 70-105VAC at 20hz is what the system is looking for.
2- The usual limitation on phones, especially with a small system like the 551 is the number of lamps that can be lit at the same time. I don't remember what it is for a 551, but you should have no problems with 8-10 sets.
3 - Intercoms come in two basic flavors: manual and dial. A manual intercom is designed for 1-2 users (though more could be added). It takes a card in the ksu and supplies talk power and an in-use lamp. Signalling is done by converting unused buttons on the set to non-locking and using them like doorbells. External buttons could also be added and spare wires in the set are used to connect to the signaled set.
A dial intercom is a separate piece of equipment that connects to the telephone sets. Usually they are single channel units (though multi channel units were produced). You went off hook on the line associated with the intercom, the lamp lit and you dialed the desired party. Signaling voltage was sent on a separate pair to the appropriate set. The only thing the intercom connected to the KSU for was power (Talk [usually filtered -24VDC], Relay [unfiltered -24vdc] lamp [10VAC] and signaling [either 18 or 10vac or ringing generator]). all other connections went directly to the tel sets.
To answer your question - yes, there is documentation, but it depends on which intercom you're talking about.

Hope this helps - at least to get you started.

Sam

51A type lamps as found in 1A2 sets draw just under 40 mils. (Mother says 0.036 mA, exactly) So you can theoretically use a maximum of 50 on a 2-amp fuse, but you may let out a little magic smoke with that many.

The station output voltages will be fine to function with 1A2 provided that the line cards are "E" models or above. 400D cards and below will not respond to ringing.

Keep in mind also that the TD1232 does not send a disconnect signal when the calling party hangs up, so calls on hold in the 1A2 will not release automatically when/if a call is abandoned.

Western Electric type 400D KTU's of issue 15 and later will respond to bridged ringing. Earlier issues will only respond to grounded ringing. They will all work reliably on loop voltages of 20 volts and up, assuming that the line current is at least 20 mils.

As Ed says, E, F, G and H versions will work on bridged ringing. Also, SanBar 4000-series will work, too.

There is a very simple bridged ringing modification that one of our TCI members has come up with to convert WE 400D cards made prior to issue 15. It involves cutting one lead and soldering in a resistor on the daughter board.

If you're interested in seeing it, I'll forward the pdf to you privately.

Appreciate all the information thus far, this certainly gives me a good base to go off of. A dial intercom seems interesting, but requires tracking down additional hardware. Assuming I can find a KSU, I'll probably start with the manual intercom first.

Arthur: I'm interested in seeing that document. A modification like that would be pretty easy for me to do.

Ed: I imagine the way around that is to manually release the call on the phone in question.

Two other things that came to mind:
(1)From the pictures I've seen, it looks like the KSU power supplies use non-standard fuses for protection. Has anyone ever modified those to use standard fuses and holders, like ACG fuses? I can't imagine it would be that difficult to implement.

(2) Given the age of these units, has anyone run into issues with the electrolytic caps? I imagine a number of the power units would need to be re-capped. Not hard to do, assuming the power unit can be opened.

A dial-selective intercom is a nice thing to play with. Look on Ebay for "teltone C-19" or "teltone T-19" They mount outside the smaller KSU's, or inside the larger ones. They use the same power feeds that are already available in the KSU.

Yes, some people, not realizing how plentiful the flat fuses are, have used automotive-type in-line fuse holders. Just bridge across the fuse screws with the two leads. A short piece of one strand of copper from a stranded extension cord makes a nice fuse wire, in a pinch. They are called "no-blo" fuses for their robustness.

I have never needed to exercise any old electrolytic caps in telephone equipment. You could bring them up to full input voltage slowly (start at one/fourth voltage, say, and bring them up over a period of a day or two) with a variac, if you're concerned. All the components are easily accessed.

I had a bad filter cap in my 551B KSU that manifested as hum on the intercom line. I found a spare PS on Ebay and plan to recap my original when I have some spare time. Its a very simple PS but odd in that the first stage cap is non polar. Why they chose to save on two diodes and go a non polar route seemed odd to me. But hey it worked...

As Arthur said, check eBay for Dial Intercoms, or maybe some of the folks on the site might have one available. The units are usually identified by a Letter and a number. T-10 is a tone only, 10 station unit. R-19 is a rotary only 19 station unit and a C-36 would be a combination (rotary or tone) 36 station model.

There are slight variations - some units offered "dial tone", most did not. Some could be converted to multi-channel, most could not, etc.

Earlier dial intercoms were large, cumbersome things. When the new models, essentially the size of a trade paperback, came out, the others all went away.

The new ones connected with a single amphenol cable. You punched them down on a block and connected power in and signalling out.

Sam

Bussman, through Newark.com, sells fuse wire from 1/2 amp to 30A on spools. Click Here Unless you know the exact gauge and conductor properties, you are taking a chance either over protecting or under protecting the equipment. It is quite easy to repair the flat fuse and they can be repaired over and over again. I still have fuse wire from the old X-bar PBX days and that was 30 years ago. A spool lasts a long time.

Rcaman

Hello,

First time I've used this or in a long time.

I need a 1A2 ATT Ring Generator or it my be called an interruptor.

Thx
Dave

An interrupter is usually a mechanical device consisting of a motor and a series of rotary disks which are cam-action operating switches.

A ring generator is an AC power supply with an output of 80-100 VAC @20 Hz. This is used to cause ringers to ring in a common audible configuration or for station intercoms.

Which do you need and for which KSU?

Rcaman

"...80-100 VAC @20 Hz..."

Or 30 Hz.

Arthur,

Correct, as usual.

Rcaman

I have ring generators and interruptors, and ksu's. Contact me off-line at vze2m645 at verizon daht net.
mm

The old relay type was a 207 c dial intc if you wanted to go that old.