The 3-wire version works with an isolated and separate rail side, which is connected to the annunciator module and connected to ground via the conductive axles of the vehicles.
Digikeijs DR5088RC DIGIDETECT Digital Occupancy Detector - Loconet. 16 Fold
Uhlenbrock GBM 43400 Track Occupancy Detector With Relay In Original Packaging
Uhlenbrock GBM-R 432 Track Occupancy Detector New In Original Packaging
LDT 8-fold Feedback Module with integrated occupancy detector
Littfinski 8-fold Feedback Module with integrated occupancy detector Kit
Mxion BM (10A 4 Channel Occupancy Detector All Systems, Adjustable Sensitivity)