Hi Ian
I have to say, I can't remember the last time I came across a hardwired old-style phone.
When 'System X' and 'System Y' (Digital) Exchanges were being phased in, approximately 25yrs ago, there was quite an upturn in staffing levels, especially engineering. This was to assist with the change-over programme, which obviously involved upgrading the EU's hard-wired connection, to the NTE5.
There was also mass activity on the Exchange MDF's, as all the
old 2-wire jumper connections from Bar/Pair to Strowger/TXE2/TXE4/TXE4A/Crossbar equipment, would in effect become redundant after the
new 2-wire jumpers to the digital equipment were made 'live'.
The way this was achieved, was by 'mapping' each MDF layer and using a system called 'Jumpering In Fast Form (JIFF). This meant the wire loom for each 'Jumper bed' could be made up in a different location, and then when completed, lain over the existing wiring on each 'Jumper bed'. (Still with me ??
).
Once this loom was in place, the laborious task of terminating each 2-wire jumper would take place. This would entail 'Double jumpering' (ie: Overwrapping) the new wire on top of the existing wire attached to the Bar/Pair. Then connecting the other side to the 'Sys X'/'Sys Y' (digital) equipment.
Once all the new 'Jumpering' was completed, commissioning of the digital equipment took place using a bit of kit called (from memory), Mobius ??. Once this was completed, the new digital equipment was made 'live'. This meant the Bar/Pair would be initially served by two different systems, so to counter this, 'Dis plugs' (Disconnect plugs) were fitted to each port of the new digital equipment. These plugs each had a hole, that was then threaded with twine and grouped together ready for the big day.
Change-over days were buzzing, as BT's hierarchy would often attend, along with other local dignitaries, plenty of photo-shoots, and then food and pub later in the day. The actual change-over moment was fraught with anguish, especially for the 'Exchange maintenance guys', and we power engineers to a degree. The call would go up, 'Out with the old' ... and the old stuff was switched out, then, 'In with the new' .... and lots of us would be pulling like mad at the twine, ripping out all the 'Dis plugs', thus allowing the new digital equipment to become the new 'feed'. This was done around 6-7am for minimum disruption.
Straight away, the tests would then be made by the 'Exchange Maintenance lads' to large PBX premises, Fire, police, Ambulance, Hospitals etc etc ...... and I have to say, I never witnessed one major service outage.
After the days excitement, the following months were taken removing the old jumper wires and tidying the MDF up.
My apologies for prattling on, but once I started to answer the initial question, I went into free-flow. Ah, memories.
PS ...... the temperature and noise (audible) levels dropped dramatically once the digital systems were up and running. The Strowger and Crossbar equipment in particular, were incredibly hot-running, and you could barely hear yourself speak at peak call-times.
