I've taken a quick look at a partially implemented signalling system on our club layout, and it looks like it uses a diode-based block detector where one feeder is split between the block detector. There's no noticable voltage drop in those sections, so I'm wondering if detection can take place by splitting a feeder and installing other parallel feeders to the bus.
The layout is DCC, but I've got no idea what vintage the block detectors are.
I don't have the part numbers to try to find the manual.
Puckdropper