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Any Switchers out There? Xbar, SxS

Started by ESalter, January 23, 2011, 09:30:57 PM

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I thought I'd post a couple pictures to see if very many of you out there liked switching.  I haven't seen much on the forum about switching before.  I figured some of you out there have to be interested.

These are all old pictures I dug up.  If anyone wants close-ups of anything in-particular or has any questions, don't hesitate to ask.

The first one is a WE 755A Crossbar PBX.  It has 4 outgoing trunks and 20 stations.  The stations are numbered 20-39.  It can have 3 communication paths at one time.  This switch is particularly neat to watch operate as it "stores" the first number you dial.  If anyone is interested, I can take a video of it operating. 

On the right of the photo is a demo SxS switch my dad and I built a while back.  It has one linefinder, two selectors and a connector.  It has 4 digit station numbers and of course "dial 9 for an outside line" which is hooked to the crossbar.  On the back wall there's an ivory painted WE 1A2 shoebox.  The black box is a WE 820D Merlin system.

The other two are of the big Strowger switch.  My dad and I put it together from AE central office pieces.  The framing was actually left in the basement of our building.  The building we are in is an old telephone office.  It used to house a Stromberg Carlson X-Y system.  When the telco moved out, they just tossed a bunch of the racks and such in the basement.  We sandblasted and repainted some of that and used it to mount our SxS equipment to.

The bottom is the linefinders, 20 switches, 10 sets of line and cutoff relays to run them(each L&CO enclosure has 2 sets of relays).  The upper two rows of switches on the left(above the linefinder switches) are selectors and the two on the right are connectors. 

For those that don't know, when you take a phone off hook, a linefinder automatically zips up and around to "find your line" and give you dialtone.  A selector steps up to the level of the first number you dial and steps around automatically to connect you to another selector(depending on how many digits the number is).  A connector steps up the number you dial and around the number you dial, thus connecting you to the line you're calling.  This system uses 3 digit numbers, so when I pick up the phone a linefinder goes up and around to give me dialtone.  I want to call station 501.  I dial a 5.  A selector steps up to the 5th level, then zips around to connect me to a vacant connector.  I dial a 0, the connector steps up to the 0(10th) level.  I dial a 1 and the connector steps over 1 and rings that station.  I apologize if that's difficult to understand, it's rather hard to explain without being able to explain as it's actually working.

The most significant part of that project so far was the linefinder shelf.  The bank of 20 switches and all of the line and cutoff relays that go along with them are on one big frame.  The original frame we had was cut in half between the switches and the relays, so all the wiring between them would have to be spliced.  Luckily, we located a complete linefinder bay.  The switches can come off to make the whole works lighter, but the L&CO relays don't.  My uncle had to help us get that in the back door of our building with a forklift!  There's a picture of it sitting on the floor when we got it and another of us hoisting it up.

Well, that's all for now.  I'll work on videos the next time I get the chance.



Hi Eric:

Yes there is at least one "wanna Be" switcher here. I removed and junked enough stuff (working for the Telco here) to fill warehouses and now I wish I had kept some of it.

Thanks for posting your pictures and telling their story. Is all of your switch gear at the office building or is some at home? Is the big switch AE or WECo?

I do have a single shelf of AE SxS switches wired into a demo unit that can process a 7 digit call. It was used in our training centre until they no longer had a need for it and then I got lucky as an installer that knew I was into this sort of thing was asked to get rid of it. It has been following me for about 25 years now.

I also have a dream to get a 200 line CDO (200 line SxS trailer from a small town) brought to Vancouver and restored to working condition. I had heard rumours of its existence and finally found it and took pictures in September 2009. Here's a link to the pictures on my Photobucket site.



Here's a PBX thread from early 2010 that gets away from the Panasonic 616 theme and onto some "Real PABX's"! So there is at least some switching interest. Maybe we need a switching category??

I posted some pictures of a "Real PABX" in this thread.



WOW!  I completely missed the pictures of that Hitachi Crossbar, that thing is cool!  Our big switch is AE.  The switch racks look incredibly similar to the pictures of the equipment in that trailer(which you better get your hands on!)  All of our stuff is at the old phone building, the house isn't quite big enough.  My dad put a comdial system in our house(because it runs on just 2 pairs), but I didn't like it.  At some point when I was in high school I put a Merlin 410 in my bedroom because I wanted to use my burgandy Merlin phone, and sometime later I added a red Trimline.

My dad used to work for a 2-way radio/telephone/alarm company.  He remembers in the late 80s or early 90s they removed a WE crossbar PBX from a local hotel.  He's always said it was a 770.  From the way he's described it, I think it was a 756.  All of it went into the dumpster except for the power supply which is now running our small SxS demo switch.  Both of us wish we could go back in time and slap him for not taking it!  It's sad how little of that equipment survived, it's such neat technology.



When I was younger, I was always amazed as to how many things a phone and Central Office could do with only a couple of wires. It wasn't until recently that I began to play with phones that I realized all that happens behind the scenes to make a call go from one phone to another.

Keep the articles coming. Even though modern electronics have reduced the capabilities of relays down to microscopic transistor based switches, nothing compares to the sounds and sights of old switching equipment.


If it wasn't such an ordeal to move almost every sort of electro mechanical telephone switch I think there WOULD be a lot more of them in basements and garages.

I have some 1A key equipment as well as some AE 10A1 and 10A2 (AE's equivilent to WECo 1A1 and 1A2). I recently rescued an Ericsson 636 PAX system (30 line cross bar Intercom) and it was pretty much all that I could handle on my own.


Dave F

Jim Stettler

I am not a switcher, However, I am interested in switches and switchboards. I do have own some switch stuff.

Last May  I asked Fred Haynes about the feasability of building me a demo step switch. I thought it sounded like a neat toy.

Fred decided it sounded like a fun project.
He hopes to have it compleated for the KS show this Spring.

I also have a step switch LAmp. I had it displayed at the Lyon's NE show.

You live, You learn,
You die, you forget it all.


Eric, that is some great stuff.

I would really like to see a video when you get time to post one.

I never worked in the frames but had to know basic theory for some of the positions I held with Pacific Bell/SBC/AT&T.  I had hoped to get inside the last crossbar CO before it was upgraded to 5E, but never managed to.   I understand that in a big CO, the crossbars could create quite a racket, which would have been fun to hear.

Does anybody know the type of switch that appears in "Dial M for Murder?"


Crossbar and Strowger offices could both be very noisy. We didn't use very much crossbar here in British Columbia but we did have 4A crossbar toll offices. I recall the one I worked at in 1977 being very noisy during weekday business hours. There always seemed to be circuits in the 4A being monitored over speakers playing the MF sounds of calls being forwarded towards their final destination.

I was working in a SxS office of around 30 thousand lines when a large cable was ripped down by a car accident. Due to the way CO's are graded and the fact that no more than 10% of the subscribers could initiate a call which would use all available line finders, the resulting shorts as the cable was ripped out caused virtually every linefinder in the office to attempt to find the lines that were calling for service. This caused a very noticible roar to go through the office on an already busy day.

I certainly do miss the sound of an office processing calls.

I don't know about "Dial M for Murder" but "Three Days of the Condor" has a scene in a working Crossbar Office. I think we discussed it on the forum previously.




I have a demo SXS that I built.  It was quite educational.  I outfitted it with an electronic "old dial tone" generator, which also provides busy and reorder busy tones.  Still working on a ringback tone generator.

It only has one line finder, one selector and one connector, so.... only one talk path, even though I have 10 line/cutoff relays.

So, I can hook 10 phones to it, but only one conversation can take place at a time.
-Bill G


I lived in an area served by a Strowger CDO when I was a kid, and worked on Ericsson XB switches in college, so the sounds of those machines *really* pull some serious strings in me.  As John Barlow said back in the day, "cyberspace is where you are when you're on the phone," and it's really true that with any electromechanical switch, there is a clear and distinct sense of being in a "place", a discrete circuit path, something that has a physical existence to it rather than being packets in a "cloud."  (I will never forgive whoever came up with that "cloud" metaphor!)  When I compare that to what's happened to the network especially over the past ten years, it's downright painful.  These machines were robust, reliable, nearly atomic bomb proof, energy-efficient (a Strowger machine uses practically zero power when idle, which is most of the night hours when, conveniently, the sun isn't shining: so therefore easier to run on a photovoltaic system in a remote area), and could be repaired down to the component level.  And they did not lend themselves to broad-spectrum surveillance or to "robo-call" telemarketing spammers. 

So I'd love to have 50 - 100 lines of Strowger equipment in operation.  I do not have a place for it now, but will in a couple of years when I'm on my own land and can build out as needed.  In fact I'd like to open up the exchange to neighbors as a kind of "living history" project that has the practical consequence of being a backup to the (usually less reliable) mobile & VOIP services that people often have now.  There is also a sliver of a chance to buy out a small rural telco and put a Strowger switch back into the CO as a backup to the Nortel DMS, but that is going to require serious capital and cooperation to make it go.  I have some ideas in mind for the "regulatory strategy" that would be needed to make something like that fly.  Basically the Strowger machine would be a "living history" project that didn't connect to the outside world, only within the community.  A similar strategy could be used to put cordboards back in service. 

Re. Panasonic:   First time I ever saw a Panasonic PBX (the original 616) I was skeptical: Panasonic's great strength was audio & video, so what were they doing making PBXs?  But I played with it and found it was as capable as a Mitel SX-20 at about 1/3 the cost, so we started installing them.  And Panasonic kept ahead of the rest of the market with features that made them flexible & robust in ways that competing systems weren't, so we got further into it with them and I got certified. 

One of the things about Panasonic that is truly unique is that they take input from the grassroots and act on it.  There are four or five features going back to KXTD-1232 r4, through the present KXTDA/KXNCP PBXs and KXTVA voicemail system, that I specifically suggested or designed, that Panasonic adopted.  The most significant of which are the external call transfer features in the voicemail systems, that enable even small businesses with as few as three employees to have telecommuters or remote employees.  I could go into that in more detail if anyone's interested.   

I can provide Panasonic equipment for folks here if anyone's interested, but this isn't an advertisement (I'll post one in the classified section here one of these days:-)   One thing to keep in mind is: the older generation machines up through KXTD series, have strong ringing output that'll ring anything.  But the smallest of the current generation, KXTDA-50, will ring most normal phones e.g. 500s and equivalent, and modified GPO 706s etc., but isn't quite strong enough to ring some phones with low-impedance ringers (high REN).  For example I have a GPO Trimphone that doesn't quite ring on my TDA-50 system.   The reason for this is that over the years Panasonic has radically reduced the power consumption of these machines, to a small fraction of what it was 20 years ago: and one of the results of that change is less power for ringing analog ringers.  However the way to deal with that is to put a smaller capacitor in the ringer circuit, which makes the bells quieter but still works. 

More later; gotta' scoot for today...


This topic always brings back memories.  When I was a kid my Dad would visit his friend (my godfather) who worked 2nd shift at the CO fixing any problems with the switches.  He was the only employee there.  And he and my father would split a six pack while my godfather ignored the red blinking lights for an hour or two.  I had the run of the place for the most part.  I remember that it was very loud, except for the battery room..  I developed quite a collection of old wire, cracked buttsets, etc.  I remember that the popular items were wasp killer and the wooden slats with the foam covers that my Mom used to clean the blinds.  I believe they were designed to remove dusr from between switching equipment.
Greg Sargeant
Providence, RI
TCI /ATCA #4409


Hi All;
I have the following Stepping units on Order (They are Paid for, Just have not arrived) and have found Documentation on 33013 and on 66414 on the TCI Library... But, I have NOT found Anything on the 65901... I hope to use these for the Start of my Own Stepping Switch.. I know its Just a beginning.. Any Help would be appreciated.. I have also posted on the TCI Forum...


Hi All;
I gave the Wrong Numbers for what I am getting... Here are the correct ones !!!!!!
connector ED 31739 (Can't find info)
selector  ED 30976 (Can't find info)
Basic Selector ED 30200 ( Can find Info)