Interesting results wiring a pair of Dapol Signals.

[Robert Stokes]

I have two Dapol working LMS signals, which when installed on the layout, will be close together (one on the up line and one on the down) but the pair will be a fair distance from the control panel. I wondered whether I needed to use two pairs of wires from the control panel to the yellow connections on the signals or whether a common return could be used. This was not just to save wire but to reduce wiring complexity and the work involved. I set up a test rig with two signals fitted to a piece of plywood with battens below to allow for clearance. All the wires were connected to a choc-block on the top. Wires from the other side of the choc=-block could be touched to operate the signals. Although the yellow wires appear identical I suspected that their purpose might not be. The choc-block connector thus had yellow wires designated LA, LB, RA, RB where L is left-hand signal and R the right-hand signal.

 

The results were interesting. With LA and RB joined as the common return, the signals operated simultaneously whichever one of the single wires was touched to the common one. With LA joined to RA as the common return and with LB joined to RB, one of the signals reacted as soon as I tried to make the connection. This meant that none of these three arrangements would be usable. However, LB joined to RA as the common return did exactly what I wanted - independent control of each signal when the appropriate wire was touched to the common one. I attached a small piece of black tape to each of the yellow wires which will form the common return when fitted to the layout before dismantling the test rig.

 

I hope that others may find this useful.

 

Robert