A Human-Sized Strowger Telephone Exchange

A large hacker camp such as EMF 2024 always brings unexpected delights, and one of those could be found in the Null Sector cyberpunk zone: a fully functional Strowger mechanical telephone exchange. Better still, this wasn’t the huge array of racks we’ve come to expect from a mechanical exchange, but a single human-sized unit, maybe on a similar scale to a large refrigerator. [LBPK]’s PAX, or Private Automatic Exchange, is a private telephone network, 1950s style.

It stood at the back of the container, with a row of four telephones in front of it. We particularly liked the angular “Trimphone”, the height of 1960s and 70s chic. You could dial the other phones in the network with a two digit number, and watch the exchange clicking in the background as you did so. Some of the sounds weren’t quite the same as the full-sized equivalents, with the various tones being replaced by vibrating reeds.

This exchange has an interesting history, being built in 1956 by “Automatic Telephone & Electric” for the Midlands Electricity Board, power generator for much of central England, where it served its commercial life. On decommissioning it went to the Ffestiniog narrow gauge railway, in Wales. He was lucky enough to learn of its existence when the Ffestiniog had no further use for it, and snapped it up.

We have to admit, we want one of these, however he makes clear that it’s an unwieldy machine that requires quite some attention so a Hackaday mechanical exchange will have to remain a dream for now.

3 thoughts on “A Human-Sized Strowger Telephone Exchange

  1. Second telephone exchange story in 3 days with a Midlands Electricity Board related comment. 1956 was post vesting so most of the generation transferred already to the Central Electricity Generating Board.. the MEB was largely distribution at 66kV and less. In the other comment I said about finding a full exchange in Summer Lane substation in Birmingham. I guess these cute little things were used at smaller depots and maybe the control rooms

  2. I grew up on a ranch on which we raised, among other livestock, hogs. When the hogs became pregnant and ready to deliver, they were enclosed in something called a farrowing pen. These were “cages” about 6 or 7 feet long, 2 foot wide and maybe 3 foot tall. The idea was for the laboring mom to be able to stand and lie down but not turn around (because sometimes sows eat their newborn). Back in the 70s, our pens were made of rails I was told came from a telephone switching network. One rail on each side. Imagine a panel 7 foot long (probably longer before being cut for our use) by 2-3 foot wide with crossbars approximately every 4 inches, and very, very heavy. I’ve never seen rails like this used in the back room of a switching station but I have no reason to disbelieve the story.

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