atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems Chaining 66 blocks with AMP connectors

@Silversam: Thanks!

@RotaryDialTommy:
This project is indeed not something a sane person would do,
it was more a learning experience and something I'd wanted to do for a while.
Cost wise, it's probably not cheaper than a 551a on ebay, but it is lighter, lol

@DimensionSeven:
Your wifi idea sounds neat. I'd actually thought about using
1a2 over wifi, but I wasn't familiar with digital to analog for voice
when it came to converting two wire to four wire. So I held back
on that project, as it took me too far into D/A, A/D telephony.
I might try that as a follow up project, though!

Of interest for 1A2, there are cell phone bridges that can connect
cell phones to POTS, and therefore 1A2. I looked into that a few
weeks ago, the box is around $100. Was curious to experiment with that.
The reviews on Amazon for the product were mixed, but promising.

One 1a2 feature I regret I didn't want to get into is an auto attendant
and voice mail, two features that have been important for my business.
Having an auto attendant feature gets rid of robocalls! I have an AT&T
1080 system with that feature, and love it just for squashing the 4 or 5
junk calls per day my business lines get.

@Arthur:
Regarding ComKey 416: yes! Some ComKey 416 features
inspired me for this project, esp DSS and intercom.

One of my folks worked at an office where they had a 416 system,
and I was familiar with its operation by talking to the head
secretary; she knew all the features, and showed me on her
primary set, which I remember was a great deal larger than the other sets.
So I was familiar with how it worked.

Later they ripped out the 416 system (early 80's), switching to
a "horizon" system, IIRC. (I recall it had a different ring, and
maybe fancier buttons?) Again, the same secretary showed me the new
system. She had noticed my interest in the phones, and thought
to rescue a 416 satellite set from being tossed out, which I still have.
Has a rotary dial. So as a young teen I studied that quite a bit.
I have a drawing I made of it on my ComKey 416 page:


Great modular design internally. Never had or found repair schematics
for ComKey phones, though, so there's a lot I don't know about their
internals. I also never got around to opening my primary set, hrm. Don't know
if I should be scared to look or not.

Some years ago I purchased a touchtone satellite 416 set, pic of it here.
..and later, bought a primary set off ebay. That was great, because
then I could actually get it all working as intended.

At the time access to ComKey documentation even on the net was limited,
but was able to find some hookup docs, and reduced it to a single document
I also posted on my ComKey 416 page.

Re: C*NET, nice; thanks for the link, and the offer to discuss stuff.
Indeed I don't find myself on the east coast much anymore; used to
live there. Not missin the cold!

When you stated "Never had or found repair schematics for ComKey phones, though..." are you talking about BSP 518-450-105?
It is available if need be HERE, unless of course you are talking about something else

Nice job, although I can't see any commercial market beyond collectors and hobbyists.

What amazes me is that you are able to have a "one of" board made for prototype purposes at reasonable cost? Back in the stone age when I was doing stuff like that I had to draft my layout by hand on mylar with stick-on tapes and pre-made pads for the components. Original was 3:1 which was photo reduced to a 1:1 negative. That was used to mask a copper clad PC board that had a photo sensitive coating over the copper. After exposure to UV light you wash the board in a solvent that removes the coating where it wasn't exposed to the light. Then you placed the board in an etching solution that ate away the unprotected copper leaving the traces. After that you cut and drilled the board then you were ready to stuff it.

There was PC board design software available but it was very expensive and as you can imagine slow on the 286 machines we had back then. We've come a long way.

-Hal

@Prof Shadow:
Wow, thanks! Yes, I've grabbed quite a few of the cowboy's PDFs, but missed that one. That's a /much/ better version of what I have, which is BSP 518-450-106 in a crappy paper xerox form. The documents are similar, but indeed the PDF has schematics I /don't/ have.. weird!
I looked thru your PDF; it has some nice info, but it's missing all the IC's and quite a bit of the logic stuff, and circuit description. What the BSP's call "schematics" I'd more call a detailed wiring diagram; they cover the relays and transformers, but not the ICs, and details of transistor circuits. That stuff gets tricky. What I'm looking for would I guess be more of a "service manual", something the guys at WE/Bell Labs would have to troubleshoot and repair the circuit beyond field repairs. Those kind of documents cover part numbers, ICs and transistor logic. For instance, I've seen some of these for after market line cards. And I think on cowboy's pages, I found an actual WE schematic of a 400D card. A full diagram including the transistors. No circuit description though. IIRC, it was a bunch of GIFs I had to paste together to get the big picture.

@hbiss:
Yes, not many markets for sure, lol.. I'm not looking for one really. Just wanted to make a professional solution to this, to see where it would take me. Bones up my circuit board skills, and I actually find it fun. One market, though very slim, would be for film/tv and theater prop rentals. I work in the film industry, and have made technical solutions for many years, though mainly in special effects. Often I see 1A2 "not done right", not only in period pieces, but even in film/tv shows of the 60's/70's/80's. The most common thing is no lights, or lights not operating correctly.

Regarding "one off" boards, most pc board print houses offer small print runs for prototypes. In my case, 2 boards for 2 layers costs around $350 to print, 4 days or so to arrive at my door. That includes silkscreen (white text) and solder masks (green coating to cover the traces to prevent shorts from stray solder). It's cheaper to do a run without the silk and solder masks.. I think about half that price? I have few other hobbies that involve cost, and no significant other to tell me to "curb my spending habits", "get your power tools off the dining room table", or "stop using the living room as a workshop" : D

I remember the "masking tape" days of early circuit design. Ugh. Had to do that back in the mid 80's -- didn't like it one bit. I actually wrote some simple CAD software (in DOS) in the late 80's to layout circuit boards and pads. Single side only, but it spit out PostScript that went to a laser printer that was sufficient for the board printers to use instead of tape up. They'd make 1:1 prints of the page onto clear acetate (kodaliths?), one for drilling, one for traces and pads. They'd include those acetates along with the boards on delivery. I recall the cost for a few one sided boards with various holes was around $180 in those days, including their printing costs for kodaliths. I think I still have the invoices somewhere. Since they "stack" the boards before drilling, one board isn't much different than two.

I do have a friend that makes his own single side boards at home from time to time, when the board is simple enough. He has jars of chemicals and whatnot; a brownish green murky liquid that eats away the copper. I've never done it. That technique is best for surface mount boards; no or little drilling. Tricky for through-hole stuff like mine though; tough to drill tiny holes accurately without a computer controlled drill press, and some of these connectors won't go in at all if you're just a little off. Single side boards also suffer in that, without through holes, the solder pads "peel off" easily. With double sided boards, there's actually a cylinder of metal connecting through each hole, which increases pad stability.

Following up on the 400d "functional schematics" that omit details vs. a full schematic; here's the 400d from one of the BSP's that is commonly found:



Now in comparison, here's a more detailed schematic; note part values and transistor arrangement details:



The transistor arrangement is important for someone studying tricks and techniques, as well as detailed part troubleshooting for dead boards. I tried to reverse engineer a 400D once, so as to make a page on how it all worked in detail, but it was too hard; reverse engineering makes me crazy unless I were to de-solder everything.. didn't want to go there. Figured I'd wait until documents turned up.. and they did!

If you know of a source for the actual WE service manuals for e.g. line cards and ComKey, I'd sure be happy to know about 'em..! I assumed they were few and far between because they probably never left the repair labs. Circuit descriptions are even more useful, as one can learn analog tricks/techniques. That patent I mentioned a few posts ago has a great circuit description, I learned quite a bit from that alone.

I had the Service Manual, Vol 2 years ago. Is that what you are look for?

Here it is: Service Manual

The Bell System, being, essentially, the only game in town, and having their own vertically integrated company, did not need to print or distribute details that could fall into the public's hands. There were no component-level field repairs expected, therefore no field repair documents.

Some engineering documents can be found, in excruciating detail, in the BSTJ, and the BTR. (Bell System Technical Journal and Bell Telephone Record.)

After that, there are SD's (Schematic Drawings...you displayed one above) CD's (Circuit Descriptions) and of course the lowest form of documentation, meant for the repair force's field reference, the BSP's.

As time went by and the repairman's job was dumbed down, the schematics in BSP's were also simplified, as you have seen, when looking at what you know to be a complicated circuit, but shows just a few block diagrams where "a miracle occurs" as the old cartoon stated.

Those of us who worked in the golden age of 1A2 and EM PBX's jealously saved and hoarded the original, detailed, BSP's and would refer to them when the "new & improved" versions didn't offer the detailed help that was needed.


[img]https://i.imgur.com/EXmmL.jpg?fb[/img]

@Prof Shadow:
Thanks! While I do have Vols II and III of the BSP's (again, as bad xeroxes.. a pile of binders about 5" thick), and recently located Vol I on cowboy's BSP site (wish I'd had that 10 yrs ago!), this is again a much nicer version than I have.. and having text-searchable PDF versions is waaay better. Also, wow, there's /color/ in some of these documents? (pp.53 of that pdf -- red arrows showing the path to ground for lightning). I should probably toss my ugly xeroxes in the recycle bin, along with the silverfish that are munching on it, and just depend on the PDFs at this point.

While it does say it's a "service" manual, as Arthur points out, there's limits on how far the BSPs go into detail. The BSP's seem to be "field service", as opposed to.. hmm, what's the term, "engineering" servicing, where e.g. dead line cards or burned out ComKey mother boards would go for servicing, to determine if they're salvageable or blown beyond repair.

@Arthur:
Thanks -- the "Bell System Technical Journal" seems like a very good lead -- that's a big rabbit hole to go down, great! Excruciating detail indeed; some of that stuff is like reading Scientific American; heavy on the math and physics of electronics and telecom.

Apparently IEEE and Nokia have teamed up to make these available as PDFs.. looks like that's a "join and pay" situation to access the articles, at least from what I gather on the IEEE page. Seems there's other providers as well. Would be interesting if they have articles focused on business phone systems and key system design/architecture. I'll sniff through the abstracts.

But I also found what I think is a "free" a way into the documents via archive.org; there's a page a bit easier to browse there, titled The Bell System Technical Journal (1922-1983); an "infinite scroll" of thumbnails of the first page of each article.

IIRC, there was a guy from England (?) here on the forum some years back who was interested in studying 1A2 design, and sounded like an EE guy who wanted to go down a similar path to the one I've been taking. I think that thread might be locked, but he might be interested in those BSTJ articles as well.

And finally, a demo video for the "1 board KSU".

When I wrap this all up into a single webpage (along with some other stuff) I'll post the link here.

Thanks. I love the video, however my wife wasn't as impressed...sheesh!