Release shafts

Barking LU Cabin controls 3 Interlocking Machines (IMR's)

Barking Main 12 Shafts commissioned 30.03.1960

Barking Sidings West 36 Shafts commissioned 30.03.1960

Barking Sidings East 24 Shafts commissioned 02.04.1960

I know how many shafts there are it's about the release shafts.

I wonder if the only sure-fire way to answer this question would be to look at the bookwiring?

Yes that would be good but is there not a basic standard that is followed (I know LU has lots of standards ACE)

LU had its own signalling standards known as "LT Signalling".

AFAIK it still does even though conventional "LT Signalling" is being superseded.

My recollection is that originally manual sites with a JNBX busbar had a single busbar. Subsequently with the introduction of protection keyswitches the busbar was sectioned so that only those signals needing to remain at danger had the feed removed when such a keyswitch was operated.
King's Cross Picc was one such site with IIRC three or four JNBX busbar sections and two or three protection keyswitches but a single release lever with two shafts. It was also a site that could be manned by a signalman with the frame technically outside the IMR.

The JNBX busbar was of course one way of doing things until it was superseded for new installations.

It would make sense that a complex site might have more than one release lever in order to maintain a service in one part while having to take a release in another such as for an incident affecting one road only.

The JNBX100 was the feed disconnected when the signalman had to manually take a release by winding in and back out the release screw in the cabin.

Your understanding is correct, Timed Hand Release BX100. I recall the old Wood Green Picc signal cabin had multiple release relays which were JNNRs, Timed Hand Release Normal Relays (controlled by the screw or remotely from Arnos Grove cabin when 'G' was in king lever) which seemed to differ from what was taught for that standard of signalling, simply JNRs.

Of course the east end of the Picc was electrically fed by the North Met Electricity company originally (offices still visible in Station Road Wood Green but changed use long ago), the only area where I ever saw blue frame 50v DEV, SEV etc relays and where there were GMRs instead of GVCRs. I presume that standard was the same on the whole extension north of Finsbury Park but at that time (1978/9) I only worked on the section from Wood Green to Cockfosters and in cabins 'G', 'K' and 'M'.

Wood Green was an RSTD site when I first worked there, a stage 1 resignalling temporary relay room built of aluminium sheet was located on the platform just outside the running SM office and connected to the cabin / relay room via 6x6 Guilflex trunking at a height of about 8' for the short distance along the platform. I was safety man watching that length of trunking from 1900 to end of traffic and from start of traffic to 0700, during engineering hours I was running, testing and terminating cables in termination boxes located in the siding and on fuse bays in the temporary relay room along with my Whitechapel new works colleagues.

My recollection is that electronic TD was installed on the stage 1 changeover shift in which we also dismantled the frame and loaded it onto a ballast train. The electronic TD had been on trial at Earls Court prior to the changeover and there were a few problems on the Sunday morning which kept some of us on site while the majority of staff had returned to depot to book off. Thus we were still present when the first reverser came in, took the route to the siding and 'disappeared' leaving the points tracklocked...............

I was just a wireman back then and in those days signal circuitry was a bit of a mystery, some chargehands would say nothing and wouldn't let anyone in the gang near the bookwiring. The way to learn was to attend evening classes at Earl's Court which I did for the last few weeks of a course but that threw little light upon the signalling at the east end of the Picc. In 1979 I left signals for telephones (my original trade) and did not return to a signal section until 1996.

I was told that a GMR was much the same as a GVCR but I don't know it for fact and of course that signalling was all replaced in the stage 2 resignalling in the early 1980s. I'd love to see the bookwirings for the original signalling. I have wondered if Cockfosters to Finsbury Park originally had electric trainstops and if that was the reason for GMRs but I don't know. Somewhere I have the details for two types of electric trainstop once used on the Underground but I have no idea how widely they were used. AFAIK they were all removed in the 1950s.

Yep, I dug out some 1950s standard signalling circuits and came to the conclusion that electric trainstops were relatively 'old hat' then as only EP trainstops were shown. At that time a GVCR was known as a GCR, that is the circuitry was identical with both GR and V proved, only the relay designation was different. I worked at many sites with GCRs over the years and expect there are still some around now e.g. Ealing Broadway and South Harrow.
The electric trainstops I have as Westinghouse F2 and F3 types being AC and DC respectively IIRC, until now I never had any idea where they were used!

siGnal, Relay and trainstop - no, I don't know either.

Y-e-e-e-s. I think the first trainstops were all electric and ISTR that the V was in use in the States with their all electric interlocking, as the alphabet came from the US.

Yes - the V was the valve in the table interlockers, with the M as the motor of the trainstop, so it became V with external air or hydraulic drive.