My vintage Strowger Telephone Exchange Demonstrator

Рет қаралды 6,804

2 жыл бұрын

This video captures the fundamentals of a step-by-step or Strowger telephone exchange. This was the global standard for almost 100 years.
I have reconstructed two small exchanges. One of these is a demonstrator that allows two telephones to dial a number and connect to the other telephone. It has two subscriber circuits and one final selector. My other mini Strowger exchange connects four telephones. This exchange has two group selectors and two final selectors. The first caller uses the primary group and final selectors. When the line is busy the next caller will be diverted to the secondary selectors.
For tone generation (dial tone, ring tone and occupied tone) I can either use an Arduino microcontroller or a genuine dynamotor. In the picture I have removed the cover of the camshaft that controls the intermittent tone sequencing. The tones themselves and the 75V ringer signal are produced by an AC generator with special windings. The AC generator is connected to a 50V DC motor.
For other vintage telecommunication stuff see my website:
wimsmuseum.jouwweb.nl

Пікірлер: 23

@g7mks383 3 ай бұрын

Thanks, a real blast from the past. I spent 30 years looking after this equipment in the Uk mainly in and around Derby. I have fond memories of those days. Many hours spent cleaning banks and changing wipers and magnets. My Farther also worked as an installation engineer installing and upgrading these exchanges.

@wwsoapbox6921 Жыл бұрын

I began my 30yr telephone career in a SxS office in Los Angeles in 1968. The sounds of a busy step office is just wonderful. Thanks for the time travel back.

@wimderkinderen1952 Жыл бұрын

Thanks. Interesting to learn that the step-by-step system is known as SxS in the US where in the UK it is always referred to as Strowger. It is fabulous technology that was the global standard for more than half a century. So nice that is relatively easy to keep it operational. A friend of mine is the curator of the JKL museum of telephony near Santa Cruz. Have you been there?

@windward2818 4 ай бұрын

What does SxS mean? Did you actually clean Strowger switches? If so, what was the maintenance schedule? I have seen the Strowger cleaning and testing bay in an exchange where the maintenance work was done. I have also seen a tech repair a wire connection using a huge electric soldering iron. Did you also have to clean the bay contact bank connections when the Strowger is removed?

@wwsoapbox6921 4 ай бұрын

@@windward2818 Thanks for asking after all this time. SxS just means “step-by-step” as the switch train was set up one dialed digit at a time. As a CO technician I maintained, adjusted, trouble-shot, and did call traces in the SxS office. Wiper bank cleaning was done on an annual basis by a team of women at night, who travelled from office to office. As I recall it took about a week or more to clean banks in one office.

@lpbkdotnet 2 жыл бұрын

Love it! Very clear, and it’s nice that you described the difference between a line finder and a subs uniselector… a lot of people miss that out!

@smzca39 Жыл бұрын

stages of step-by-step or Strowger telephone exchange - a- preslecter ( for sub number ) b- 1st selector for first digit c- 2nd selector for second digit d- 3rd selector for 3rd digit e- final selector for 4th and 5th digit for five digit telephone number like 41356 - this was in 1958 when I was working in Pak Capital Telephone Exchange - Karachi for rotary telephone sets

@purplepioneer5644 Жыл бұрын

This was a fantastic explanation of how everything works.

@bboogaar Жыл бұрын

I worked in Northern Electric steppers. They were the same design as those from Western Electric. The switches you’re demonstrating were used in customer premises PBX and PABXs here in Alberta.

@jerryrobinson7856 Жыл бұрын

Autodidact in the making...At 12 years old, I Bought a step by step switch pulled from service from Edmund Scientific (or perhaps Allied) as a surplus part. Had it up and running quickly and you learn by doing and seeing. Watching a copper slugged relay was a learning curve in physics in timing a relay that when the power dropped, it held for a moment which was used and knew that you stopped dialing a digit for the wiper up count and the delay between dialing connected you to the next electromagnet to wiper horizontal. I remember connecting an amplifier to out home POTS line in a Village with a crossbar switch and for some reason it stopped the ringing like you picked up yet it must have been simulating that got the wrong number and talk power was live. When calling from a pay phone you would get your money back yet could talk for as long as you want. I learned to hook up an amplifier to listen to the line noise or dialing and ringing action, that you needed a capacitor in series.

@sxsphil Жыл бұрын

Very nice demonstrator system, great expiation.

@colmornane5684 Жыл бұрын

Great explanation of an old style telephone exchange. I have two old wall dial phones I would like to connect together and have them work as they did when these exchanges were in operation, this is the reason I saw your video. Obtaining this equipment seems to be a challenge now. Great video well done.

@wimderkinderen1952 Жыл бұрын

I understand that you are in Australia? Most of my Strowger stuff I got on eBay in the UK. To connect two telephones you only need a final selector, a couple of uniselectors and two sets of line relays. The rest is today’s electronics. You could contact a few eBay sellers in the UK that may have spare items: marglen, autofloor, newsandels. They can send copies of diagrams as well. Alternatively, you could get an electronic housetelephone exchange from the 1990s. You buy them second hand for a tenner or so. They will work with pulse dialling and also have the ring signal and all the tones. Good luck!

@G5STU Жыл бұрын

Fantastic video

@4maart1953 2 жыл бұрын

Knap filmpje, Wim. Interessant!

@highintensity Жыл бұрын

Hello Wim, Excellent video! I would like to build something similar (particularly the canned version of the subs line circuit) Would you have any diagrams of how it was built particularly with just two boxes! Kind regards, D.

@Albaloshi88 Жыл бұрын

I worked on F1 automatic telephone exchange in mid 80s made in czhecosalva

@kevinstaddon8517 2 жыл бұрын

Just tried your site but not found. Shame as I like and would like some more information on setting up and wiring etc

@wimderkinderen1952 2 жыл бұрын

Kevin, You should find the diagrams here: github.com/Godefridus/Arduino/blob/master/StrowgerSelectorDiagrams.pdf More information on telecommunication equipment here: wimsmuseum.jouwweb.nl If you want to dig further into Strowger technology try to get hold of the book Telephony Volume 2 by Atkinson. There is also a lot of information here: thg.org.uk but you need to become a member to get access to the archive of diagrams.