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Phonesrfun's Step by Step demo switch

Started by Phonesrfun, November 26, 2009, 08:05:24 PM

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Tonyrotary

I remember as a young kid reading a book about how telephones worked and was amazed at just how complex all those switches looked. The book broke it it down pretty simply but also showed a small part of a central office and it was mind boggling to think all those wires were connecetd by hand to all those switches.

rp2813

I love the scene in "Dial M for Murder" where they show the switch operating as the telephone is being dialed.
Ralph

Phonesrfun

#17
Just wanting to see if I said "Boo" if anyone would jump.  It's been pretty quiet lately.  I haven't helped much either because of my work schedule lately.  I have also been working on my S x S switch in my otherwise "spare" time.

Here are a couple of pictures of the better version.  Some may remember the version I had laid out on the floor.  I have been working on a more presentable arrangement.

-Bill Geurts
-Bill G

McHeath

I'll jump. :)

That's a pretty cool gizmo you got there, and I have no idea exactly what it does or how it does it, but it certainly looks impressive.  Various places I've worked over the years have had things like this in some back room someplace, some of them even made clicking noises as I recall. 

Dan

Hi Bill--gotta elaborate on what gizmo you have there....
"Imagine how weird telephones would look if our ears weren't so close to our mouths." - Steven Wright

Wallphone

I'll let Bill explain it but this is part of some switching gear. It is called AE (Automatic Electric) Step by Step. It was used to automatically complete the phone call. Before that you had operators using switchboards. Now everything is done electronically.
This YouTube video will give you some idea on how they worked.
> http://www.youtube.com/watch?v=wcFpaI1Y_SE <

Dougpav

bingster

= DARRIN =



McHeath


Phonesrfun

They are pretty noisy when they are being operated.  These switches were designed early in the 20th century.  They are named after the guy who originally came up with the idea of a dial phone by the name of Strowger.  The "g" in Strowger is pronounced like the G's in George.  "Stro-jer", if you will.  The switches in my photo were made by Automatic Electric in the 1950's

Anyway, the dial of the subscriber's telephone directly activates the relays and stepping magnents to step the switch mechanisms up and over, corresponding to the digits dialed.  One switch handles one digit of a number, except that the last switch handles the last two digits.  

So a 7-digit office needed a line finder, 5 selectors that each handle one digit, and a connector that handles two digits.  This train of switches was tied up during each call, and so there needed to be that many switches available for all the possible conversations that could be handled at any one given time.  In today's terms, it is a real inefficient way of placing a call, but back in the early 1900's it was one of only a couple ways of doing it automatically.

You can imagine how many switches and other equipment a  large 10,000 or even a 100,000 line central office had to have.  Being mechanical, they also required a great deal of maintenance.

None of these are currently in actual service that I know of.  All of these electromechanical switches have been replaced by electronic switching, and are actually computers.

There were two other common electromechanical switching types other than Step-by-step.  They were called Panel and Cross-bar.

-Bill Geurts
-Bill G

Doug Rose

Hey Bill....you proved you can teach an "old Doug" new tricks. I've been collecting for 30 years and never knew the correct pronunciation of Strowger. .....thanks....Doug
Kidphone

Wallphone

Another name that is probably mis-pronounced is "Leich".
Leich is pronounced "Like" not "Leech).

Dougpav

bwanna

bill, i admire your talent in building your S x S switch.  there is a small CO near here that was a "step" office until fairly recently.  i'd have to check with the old timers on the date.
donna

Phonesrfun

Wow, I am amazed that there was still a step office until recently.  Probably a very small town or something that did not have the cash to convert.

There are probably some PBX steps still around, but to be sure they are few and far between.

-Bill
-Bill G

bwanna

#28
by recently i mean with in the last 25yrs.  a very small office, not sure the number of subscriber lines, but the building is less than 1000 sq ft in size.
donna

Phonesrfun

A couple of the small towns around here have very small brick buildings that serve the local towns and they are satelites off of the switch that is in Walla Walla, WA, the town I live in. 

One example is Milton-Freewater, Oregon which is about 8 miles away, and in another area code.  Walla Walla, WA is in the 509 area code, and it drives the M-F switch in Oregon which is in the 541 area code.  Local Qwest customers can dial a M-F number as a 7 digit number and vice versa, and I believe it is a local call.  I am not sure, since I am on Vonage and although all calls in the US, Canada and most other places are not toll calls, I still have to dial a M-F call as 10 digits.

-Bill G