Re: [General] Information about block working

[Eddie Oliver <eoliver@efs.mq.edu.au>]

Ronald BESDANSKY wrote:
> 
> Thanks Eddie, but I still don't have an answer to my original question - in
> ORDINARY working, where a double line worked by block telegraph becomes a
> single line worked by OTS, under what conditions can the signaller at the
> box at the transition point accept a train from the box in the rear on the
> double line section?

The reason you don't have an answer is fundamentally because there isn't
a unique answer - it depends on the layout of the signalling at the
individual location. For instance how many signals are on the double
line before the junction? How far is the last of these away from the
junction? Are there catchpoints? Is there an outer home on the single
line? 

However the simplest example, at least if you want to design a model, is
to assume that there are two signals on the double line before the
junction. Call the outer one A and the inner one B. Then you could give
line clear to the box in the rear on the double line provided the line
is clear to B. This is then sufficient for the train to come as far as
signal A.

Then the interesting question is when you can allow the train to pass
from A to B. The conditions might be like
"Line is clear to the catchpoints and the catchpoints are open , OR line
is clear to the outer home signal from the other direction and the
catchpoints are closed". If you adopt the latter option, you would then
not be allowed to open the catchpoints again until the train has been
brought to a stand at B.

If you work on the principle that you can't have two moving trains
approaching each other with only one intervening signal facing each
train, you'll be pretty much OK. 

Eddie