British crossbar telephone exchange being installed (1970s) - Page 1
Forum section: electronics / general

author: eti
author_rank: Super Contributor
timestamp: November 30, 2019, 04:36:20 am
content: I thought you'd like to see something different and refreshing:http://www.aeolian-hall.myzen.co.uk/strowger.htm#CrossbarStrowger uniselector operating (audio):http://www.aeolian-hall.myzen.co.uk/pabx3.wavMore

author: German_EE
author_rank: Super Contributor
timestamp: November 30, 2019, 10:27:21 pm
content: I remember being shown that movie at school, but for all of the wrong reasons. The technical content was so low and the teachers were unable to answer so many of my questions that I ended up knocking on the door of my local telephone exchange seeking the answers I needed. The staff there were very surprised but quickly became quite helpful once they realized they had a junior engineer in their midst.That was a long time ago. Now a local child seeking the same information would be turned away, either because of over enthusiastic health and safety rules, data protection or 'terrorism'.

author: mikerj
author_rank: Super Contributor
timestamp: November 30, 2019, 11:08:26 pm
content: When I was maybe 11-12 years old we had a neighbor that worked for BT and he took me to a local Strowger exchange to see it all working. I remember watching the (very noisy) selectors all working away and being surprised the dial tone was generated by a motor driven device, which seemed very crude even back then (early 80's). He also supplied me with all sorts of interesting switches and relays for experimenting with. Exchanges in the UK were just starting to be replaced with the digital based System X at the time.

author: eti
author_rank: Super Contributor
timestamp: December 01, 2019, 02:48:46 am
content: Quote from: mikerj on November 30, 2019, 11:08:26 pmYour childhood shares some parallels with mine; I too had, and have, a friend who works for BT (a 2 min walk from here), and he would often give me boxes brimming with decommissioned GPO 706 dialphones & other goodies (and a Chesilvale "buttinski" BT-branded test phone - lunchbox type). Also, our little village UAX is directly behind my old primary school, and I'd sometimes go down the track at night, simply to listen to the mysterious, romantic chug-chug-cla-cla-cla-cla-KLUNK of the Strowger gear. I recall the dim, coloured status bulbs glowing mysteriously through the mottled, wire-reinforced glass panes high up on the walls of the building. I have MANY BT tales to tell, one of which is that when they converted that UAX from Strowger to Ericsson System Y in the 90s, I was given free access to the goodies stripped and dumped in the skip outside the back door, which, with hindsight, I wish I'd kept - one of those was a FULL ringing generator rack + all cams and relays etc!I was given various other exchange tours within the local area, and whilst I recall, was also given a tour of the "Express lifts" tower in Northampton, with my Dad, which was HUGELY exciting to a very young me (slipped that in before I forgot!).I was OBSESSED with telephones and exchanges during the 90s. I'd often "war dial" manually, late into the night (this is before I even knew of these terms, OR of anyone else doing it; I was oblivious!) and write down "interesting numbers", two of which are still in operation at our exchange (one is a test tone number; not "175" but a local line with STD). I also recall the birth of BT's "17070" SALTS test access, early 90s, long before most people would have even been aware that it existed, and used it extensively to "do various things" hah! I had a contact or two at BT (having dialled many numbers and having a very inquisitive mind), one of whom was a very kind and patient gent who I'd call once a week or so, and probe with DEEP questions as to timings and voltages of the BT PSTN; poor bloke - he must have got fed up of hearing my voice!!Also, I recall sending off for catalogues from the aforementioned "Chesilvale Electronics" of Newport, Gwent, and also an American company named "Teltone" who manufactured telephone line simulators, amongst other things, and also the "MT8870" DTMF decoder IC (& variants), and they'd send me HUGE application note books, which I drank in like water.I have more stories like this to tell, but not the time in which to tell them.

author: duak
author_rank: Super Contributor
timestamp: December 01, 2019, 08:47:58 pm
content: I was already interested in science and electronics when I got a tour of the local telco exchange when I was in my early teens. I always wanted a Strowger switch but other than playing with it, what else could I use it for? Maybe a calculator. A year or two later a chum & and I were walking by the exchange and saw they were turfing out some old electronics. We got permission to root thru the bin and pulled out a bunch of vacuum tube compander and filter modules and a few small relay chassis. No Strowger though. The modules were hand wired using turret posts on punch phenolic boards had some really spiffy precision caps and resistors and various bits of hardware that I used for years to make other gizmos. Oddly enough, an ARRL handbook from a few years before had the rough specs on some of the tubes. I recall that they had 48 V heaters and the pins were gold plated.