ATM 50/7A PAX (My new telephone exchange)
Yesterday, Ian and I drove from Bristol to Porthmaddog in Wales to the Ffestiniog Railway to collect a small(ish) telephone exchange or PAX (Private Automatic Exchange) The railway were having a bit of a clearout, so while we were there we piled a load more stuff in the van. Probably more than we should have really!
(The big grey box at the bottom of the van is the PAX)
It was a long drive home, so we didn’t unload the van immediately. Instead Ian came over before work this morning to help me get the PAX out of the van. After a lot of effort, we managed to get it into my lounge, where I can work on it until I no longer need to get to the back of it. Once it’s all working, I’ll move it into an alcove where it’s less obtrusive and disguise it by putting a pot plant on top of it or something.
It’s a 50 line automatic exchange with 7 connect circuits (although I’ve only got enough selectors to populate 4 of them) once fully populated it can support up to 7 conversations at once. It’s equipped with tie-line circuitry so I can connect it to other exchanges. I’m hoping to use these to hook it up to the internet so that other people with similar exchanges can dial into it.
The selectors are all 2000 type strowger selectors, which are familiar to me from the exchanges I help to look after at the Dean Forest Railway. I’ve spent the evening fiddling with it, checking things over and cleaning relay contacts. After a thorough visual inspection I bravely hooked up a set of batteries and jacked in the best of the selectors. With very little fettling, it works! So I’m already 25% of the way there!
All the phone numbers are 2 digit numbers, in the ranges 20-29, 30-39, 40-49, 50-59, 60-69. When you dial the first digit, the selector steps up that number of positions. When you dial the second digit, it steps in that number of positions. In the video below, you can see me dialing 68 and see the selector step up 6 places, then in 8 places.
I just love the noise these exchanges make! I can’t wait to sort out the rest of it!
Jealous!
“I just love the noise these exchanges make!” Indeed, the sound is the best part of electromechanical switching, and brings back memories of 50 years ago. A charm modern electronics will never know!
Hi,
I used to work for ATE and then Plessey 1961 – 1969.
Used to maintain the 10/2A and 50/7A amongst others.
Had to take the top off the 10/2A to adjust those unis!
Keep up the good work
Regards
Heh! I agree, taking the top off makes working on the 10/2A so much easier!
I heard a rumour that Cilla Black (Or Prescilla White as she was then) used to work for ATE, wiring up equipment looms. I’d love to find out if that’s true (and if so, when she worked there or what equipment she worked on! The chances of her doing any of the wiring for my PAXes are minimal, but it’s a nice thought!)