Signal Module

On conventionally controlled model railways, it is standard practice to stop a train at a signal by removing power from a section of the track. With digitally controlled model trains, an auxiliary circuit must be used to prevent the locomotive decoder from losing operating power when the train is stopped.In conventionally controlled model railways, a switch or relay is used to disconnect power from a section of the track. The train then comes to a stop on the ‘dead’ section. After power is restored to this section of the track via the switch or relay, the train continues on its way.A consequence of this approach is that the front lights of the locomotive, and possibly also the lights of the first car after the locomotive, are extinguished. However, this is accepted as a necessary inconvenience.

Resistors:
R1 = 1kΩ2
R2 = 12kΩ
R3 = 1kΩ
R4 = 1Ω2/1W
Capacitors:
C1 = 220µF 35V radial
C2 = 4nF7
Semiconductors:
D1 = 1N4001
D2 = 4V7zener diode
T1 = BC547
T2 = TIP112