Block signal protection was afforded in each direction on either track of the Hill, and 'automatic train stop' further safeguarded movements. Track magnets rose between the rails at each signal; there had to be current energizing these magnets even in clear position, or they would automatically act to cause apparatus on the engine to apply train brakes. When trackside sources of power failed, wet batteries were cut in.

As a side note, Cab Forwards were gone from the Hill some eleven years before his birth.
I'm surprised at his amazing knowledge of the subject.

CRY