Semaphore Switcher Current Operated DAP4-BR

BLOCKsignalling DAP4-BR


The Semaphore Switcher DAP4-BR is based on the BLOCKsignalling Block Occupancy Detector BOD1 (see:, but with the added ability to operate semaphore signals.

The module monitors the rails for traction current, and when it is detected, it switches the attached signal from danger to clear.  For DC layouts, only trains travelling in the correct direction will trigger the signal.  For DCC layouts, the signal must only be approached from the front, as trains approaching the signal from the rear will also trigger the signal.

After a pre-programmed time (default 5 seconds) the signal will switch back to danger.



The Dapol signal has two yellow wires. 

Connect one yellow wire to C1 and E2.  Connect the other yellow wire to C2 and E1.

The red and black wires connect to a 16V AC supply.

The track connections are made from the track supply (throttle) to the other side of a rail break.  If the module is triggered for trains travelling in the wrong direction, simply swap the TRKIN and TRKOUT connections on the module.



When first used, the module needs to be configured to run the new program (program 9).

The Dapol signal may be at clear or at danger when first powered.  If the signal is at clear, press the button on the PCB to switch it to danger.  This is only possible when there is no train on the line, as otherwise the software does not monitor the switch.

Provided the signal is at danger when the module is switched off, the signal will stay synchronised with the module.

If the module is re-powered with a train in the section monitored by the module, the signal will operate once between danger and clear, then back to danger again. It will then operate normally.



The diagram below shows the operation of the outputs when program 9 is selected.

The trigger time and release time can be adjusted if required (see BOD1 instructions for how to accomplish this).

The time the Dapol signal remains clear is set using a new setting (see programming diagram below).


Other Notes

If the module is running the lamp test, the signal will operate repeatedly between clear and danger.


Program Flow Diagram

The diagram below shows all the programming options.

Programming is performed holding down the Push Button when switching on the power.

The red led on the PCB flashes at 1 second intervals.  When the required number of flashes is seen (see later for the list of possible choices) the button is released to store the first value. At this point the led comes on for five seconds to confirm the value is stored.

The led then starts flashing again, and this time the button needs to be pressed to store the second value.

Once the two values to be stored are entered, the led flashes 10 times rapidly, and the module starts operating.

Most values entered can range between 1 and 255 (see below for limits).  If more are seen, or the programming is aborted by switching off, then the programming must be repeated.

Following the diagram is a detailed explanation of all the settings.