I have now acquired some more information from a third party which suggests:
1. The LU Signalling Design Handbook has a section on CTs which would be worth utilising as an Exam standard.
2. Control Tables are not always utilised but are often included in the bookwiring to supplement the written circuits , but these are sometimes regarded as sufficient by themselves to define the controls. Apparently the Bakerloo and the East end of the District line are good places to look.
Tend to be regarded as more essential where interlocking is implemented by data or within relay interlockings; West Ham is suggested as a recent example worth referring to.
3. If the site is mechanical, LU always provides a locking table (in addition to the locking diagram which shows HOW the locking is implemented). This covers route interlocking (i.e. signals and points), but not route locking (approach / backlock), track locking or proving.
4. It is suggested that it is very possible to produce a locking table in exam conditions. Recommendation to avoid point-point locking (unless wide to gauge traps) as this tends to lock up the site in failure conditions- may be regarded as the difference between a Pass and a Distinction answer.
State assumptions where it is possible to implement route locking either mechanically or electrically; for example back-to-back was traditionally done mechanically but nowadays the preference is just to do at aspect level to avoid excess disruption if a failure occurs.
5. It is suggested that LU actually do often see Control Tables as tabulated circuits, so details of the technology of implementation can be relevant in that context; in fault scenario there is a difference between 200VCR up and 200VPR down and this might be a rationale for showing as such rather than the more conceptual 200V "on".
As ever, put 3 signal engineers in a room and get 4 opinions!
1. The LU Signalling Design Handbook has a section on CTs which would be worth utilising as an Exam standard.
2. Control Tables are not always utilised but are often included in the bookwiring to supplement the written circuits , but these are sometimes regarded as sufficient by themselves to define the controls. Apparently the Bakerloo and the East end of the District line are good places to look.
Tend to be regarded as more essential where interlocking is implemented by data or within relay interlockings; West Ham is suggested as a recent example worth referring to.
3. If the site is mechanical, LU always provides a locking table (in addition to the locking diagram which shows HOW the locking is implemented). This covers route interlocking (i.e. signals and points), but not route locking (approach / backlock), track locking or proving.
4. It is suggested that it is very possible to produce a locking table in exam conditions. Recommendation to avoid point-point locking (unless wide to gauge traps) as this tends to lock up the site in failure conditions- may be regarded as the difference between a Pass and a Distinction answer.
State assumptions where it is possible to implement route locking either mechanically or electrically; for example back-to-back was traditionally done mechanically but nowadays the preference is just to do at aspect level to avoid excess disruption if a failure occurs.
5. It is suggested that LU actually do often see Control Tables as tabulated circuits, so details of the technology of implementation can be relevant in that context; in fault scenario there is a difference between 200VCR up and 200VPR down and this might be a rationale for showing as such rather than the more conceptual 200V "on".
As ever, put 3 signal engineers in a room and get 4 opinions!
PJW