30-09-2015, 09:42 PM
Now having had some sleep and a chance to review...
Firstly some errors in my original control tables; namely the omission of any trainstop proving, which would be done via the pick-up of CD and CG track circuits respectively.
119's should also require the timer associated with DB occ to be proved at zero as a miscellaneous control, and the requirement for CF occ for 15 seconds should really be CE clr. CF occ for 15 seconds to prove a short train suitable for coupling. Whoops!
Taking PJW's suggestions above, some commentary on the provision or omission of control tables. These were originally a separate drawing, not included in the wiring diagrams, and used to be provided simply for the RI submission. The 1950s resignallings tended to then develop them into what became 'selection schedules' - simply a circuit expressed in written format rather than drawn, and quite possibly done after the circuits themselves were finalised! Some of these have now not been kept up to date, others have been redrawn more as 'proper' control tables. Ealing Common for example has the selection schedules, and Watford South Junction has them redrawn more as a control table.
The 1970s non-safety circuits had a form of control table showing what routes had to be normal at a non-vital level - mainly because the drawings themselves were massive and hard to read quickly in failure conditions.
The Bakerloo line had a rather comprehensive set of 'used in' and 'proved in' tables for treadles, timers etc, but never really any control tables - again they were done for the RI but never made it into the site book. Anything post 1991 tended to have control tables along the NR format, so the Central, Waterloo and City lines, West Ham, Heathrow T5 etc.
The pros and cons of point to point locking are still a subject of debate in the LU community; in my early days as a maintenance tech I worked on the Bakerloo which had very limited point to point locking for the reasons PJW states; the downside of this is that the signal to signal locking often has to be more complex with greater conditioning and occasionally has to use a 'route lever' (effectively a phantom signal) to simplify the mechanical locking arrangements. As ever, it often comes down to which design team produces the design.
On that note, I am shortly due to commission a mechanical locking alteration which when I first looked at it lacked point to point locking (it was never provided and the locking was achieved signal to signal), but the designers subsequently changed their minds and provided the point to point locking. I think a lot of it, rightly or wrongly, comes down to the preference of the approver at times.
If anyone wishes to look at a set of LU control tables as used for RI submissions of the past, a good example is on pg53 of Green Booklet No.19 - this also has an example of a point control table, which is somewhat basic! The Green Booklet is also quite good at laying out the general principles of the call (the USR), the route interlocking relay (UR), and the lever operation circuit, which also has to prove the lever positions and mimic the mechanical interlocking to prevent jamming. I'll try to get a scan in the next day or so.
Firstly some errors in my original control tables; namely the omission of any trainstop proving, which would be done via the pick-up of CD and CG track circuits respectively.
119's should also require the timer associated with DB occ to be proved at zero as a miscellaneous control, and the requirement for CF occ for 15 seconds should really be CE clr. CF occ for 15 seconds to prove a short train suitable for coupling. Whoops!
Taking PJW's suggestions above, some commentary on the provision or omission of control tables. These were originally a separate drawing, not included in the wiring diagrams, and used to be provided simply for the RI submission. The 1950s resignallings tended to then develop them into what became 'selection schedules' - simply a circuit expressed in written format rather than drawn, and quite possibly done after the circuits themselves were finalised! Some of these have now not been kept up to date, others have been redrawn more as 'proper' control tables. Ealing Common for example has the selection schedules, and Watford South Junction has them redrawn more as a control table.
The 1970s non-safety circuits had a form of control table showing what routes had to be normal at a non-vital level - mainly because the drawings themselves were massive and hard to read quickly in failure conditions.
The Bakerloo line had a rather comprehensive set of 'used in' and 'proved in' tables for treadles, timers etc, but never really any control tables - again they were done for the RI but never made it into the site book. Anything post 1991 tended to have control tables along the NR format, so the Central, Waterloo and City lines, West Ham, Heathrow T5 etc.
The pros and cons of point to point locking are still a subject of debate in the LU community; in my early days as a maintenance tech I worked on the Bakerloo which had very limited point to point locking for the reasons PJW states; the downside of this is that the signal to signal locking often has to be more complex with greater conditioning and occasionally has to use a 'route lever' (effectively a phantom signal) to simplify the mechanical locking arrangements. As ever, it often comes down to which design team produces the design.
On that note, I am shortly due to commission a mechanical locking alteration which when I first looked at it lacked point to point locking (it was never provided and the locking was achieved signal to signal), but the designers subsequently changed their minds and provided the point to point locking. I think a lot of it, rightly or wrongly, comes down to the preference of the approver at times.
If anyone wishes to look at a set of LU control tables as used for RI submissions of the past, a good example is on pg53 of Green Booklet No.19 - this also has an example of a point control table, which is somewhat basic! The Green Booklet is also quite good at laying out the general principles of the call (the USR), the route interlocking relay (UR), and the lever operation circuit, which also has to prove the lever positions and mimic the mechanical interlocking to prevent jamming. I'll try to get a scan in the next day or so.