LocoNet supports up to 4096 track sensors. Sensors are generally numbered on the basis of 256 sensor boards each of which can have 16 sensors: 256*16=4096. This convention comes from the BDL168 detector having 16 inputs, and having to be assigned a sensor board number when set up.

On the South Downs Railway we have sensor messages generated by DAC20, BDL168, DTM30 and SIGM20 devices. To keep a record, here is the list of sensor numbers in use:

Board type Board number Sensor number(s) Purpose
SIGM20 serial 65 20 1-8 Track occupancy sensors, from BD4
BDL168 21 1-16 Track occupancy sensors
BDL168 22 1-16 Track occupancy sensors
BDL168 23 1-16 Track occupancy sensors
BDL168 24 1-16 Track occupancy sensors
BDL168 25 1-16 Track occupancy sensors
BDL168 26 1-16 Track occupancy sensors
BDL168 27 1-16 Track occupancy sensors
BDL168 28 1-16 Track occupancy sensors
BDL168 29 1-16 Track occupancy sensors in Portsmouth goods yard
BDL168 30 1-16 Track occupancy sensors in Portsmouth goods yard
DAC20 serial 2 161 1 microswitch on Eastleigh lift-up section. ON when flap in normal position.
DAC20 serial 2 161 2-5 Track occupancy sensors, from BD4
DAC20 serial 4 158 1-4 Track occupancy sensors, from BD4
DAC20 serial 684 159 1 microswitch on Portsmouth lift-up section. ON when flap in normal position.
DTM30 160 1-4 interlocks with DTM30 at Eastleigh
DTM30 160 5 button press to signal traincontroller to start oil train schedule
DTM30 160 6 A "toggle" button to signal traincontroller that track 1 is/isn't available
DTM30 160 8 A "toggle" button to signal traincontroller that track 2 is/isn't available
DAC20 serial no. 6 162 1-4 Track occupancy sensors, from BD4
DTM30 ser 457 163 1-16 DTM30 special functions triggered by button presses
DTM30 ser 457 164 1-4 DTM30 interlocks
DTM30 ser 457 164 5-8 DTM30 special functions triggered by button press
DTM30 clanfield 165 1-4 DTM30 interlocks
DTM30 clanfield 165 5-7 & 9,10

special functions: platform 3-1 access & schedule requests

TXC1 240 1 reports occupied while turntable is turning