alexgoei Wrote:Hello Peter,
Gone through your review comments for this year's paper and have some questions.
Thank you and Regards
There are 2 overlaps for 112B(M), the first to the POL towards the sidings and the second (which I would regard as the non-preferred) out to the Passenger Loop.
The first requires 303N (trapping), 304N, AA clear.
The second requires 303N (trapping), 304R, BA clear, AA clear.
Hence when written in combination the requirement is:
304 [written in the N or R or swinging column]
303N, AA clear, (BA clear or 304N)
You may find it an odd way of writing the logic- it is because as I have said the CTs still have the presumption of relay circuits embedded within them. SSI data would consider there were 2 overlaps and put a positive statement of which each needed (part of my fight to update 11202 to relect- I am winning but not there yet!); RRI has a single aspect relay and effectively puts in a long series path anything that may be needed in any overlap before puttting in parallel paths around various elements to condition them out when not needed. A good exercise in Boolean algebra......
PJW