Thursday, 16 July 2020

PAX Problems- a report for Strowger Nerds

No pictues I am afarid, the pax units have always looked the same!

Tuesday July 7

Paul and I had been called in to investigate a alarm caused by a blown fuse on the Winchcombe Pax and also a lack of dialling tone at Todd pax.
These two Strowger Paxes' were built by AT&E of Liverpool in the 1960's so they are a bit vintage.
They allow phone calls from all over the network but they seem to be used mostly for stations to report train departures up to Toddington using the 2 tie lines provided in each direction.
 Unfortunately the blown fuse had locked out the line circuits supplying all four tie lines!

Friday July 10

Off to Todd to look into the "missing Dial tone" and hoping that the problem was not to do with the tone generator.
 Although these are standard PO Ringer 2a's, the way they have been grafted into the AT&E units is non standard and we have no diagrams for that part of the arrangement.
 Interestingly, the original vibrator generator is still there in position ( they were used as standard in smaller systems such as UAX 12's)
The report was correct, there was no Dial Tone, because there was no start signal to the ringer, but why?.
These units were never fitted with malfunction alarms ie release or fuse alarms ( Winchcombe does have a visible fuse alarm system since it can be checked more easily from the yard). In the event of a rotary magnet being energised for two long, a relay which has specially wound coils would operate  and reduce the magnet current to a safe level. However what had happened was that due to a recurring line fault, the rotary magnet fuse on every selector had blown, leaving them all "off normal". Since there were no other selectors to seize the whole unit had come to a standstill!

So having got Todd pax working again it was back to Winchcombe to see what was happening there. We found that the fuse blowing was only on the first tie line!  We have had to leave that "busied " for now awaiting out next visit. This was 19 so 10 is still available for calls from Winchcombe area towards Todd.
 Watch this space, if you are still awake! Next visit  on  Tuesday 21st 

Mike Stephenson and Paul Dinucci


  1. Mike & Paul, thanks for the update but this was like another language to us!These faults occouring are they because the system is vintage? If so would it matter if the telephone system was brought up to date with a modern system? Only asking it seems this might be important for the running of trains,or are we missing something? Anyway, good to know S&T are on the case, well done.
    Paul & Marion

    1. Well yes, the system is old but since I have been looking after it we have had very few exchange problems especially since we have embarked on a program of replacing external cables and getting rid of many joints installed in the early days when cash was even tighter than now, thanks to covid.
      We do have a good stock of spare parts.
      Thanks for your interest
      Mike S

  2. 16 years a strowger Technical officer in a very big GSC exchange that was modernised in 1998 and I am still fascinated by the old mechanical voice switches - not the most reliable of systems, but endlessly challenging to keep working!! - glad to hear of the old systems still being maintained despite the challenges they present!!

  3. After I had done my Y3yc in London Central based at Euston and then at Canonbury/ Dickens, both of course part of the London Director system. I managed to get a transfer up to Northampton. I was a a bit taken aback the first time I met UAX12's and 13's!
    Still it stood me in good stead for these little units
    Happy Days with a Morris Minor Van!
    Mike S

  4. Please look after the vintage strowger kit, Malcolm Walker will recall me as the lad from Gloucester who joined the cables & dropped off some electric locks & cabinets,

  5. Thanks, its a pleasure to keep this old kit working well
    Mike S

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