Sometimes the engineer is distracted and routes a train into a track switch when a train is already over the switch. For train safety, the tracks leading to a switch need to turn track power on only when the switch is clear.

Three-Rail Innovations' Two Relay Controller is connected to allow only one train at a time to approach a track switch.

The following drawing shows the 2RC configured to turn off track power so one train won't run into another at a track switch.

Train direction is as shown. A single train entering either switch leg will activate the relay controlling power to the switch leg and be passed over the switch. The relay remains ON until the train clears the "Trailing Track Block."

When a train enters the opposite leg while a train is still traversing the switch, track power is off and the second train coasts to a stop before reaching the switch. After the first train clears the "Trailing Track Block" the second train is powered and moves through the switch.

The "Trailing Track Block" may be as long as needed for one train to clear another. The jumpering may be changed to increase "hold time" and allow a leading train to clear the track before a second train is started.

Isolated outside-rail and isolated power track blocks are installed on each leg of the switch. The track blocks leading to the switch are at least "coasting distance" long, so a train entering an unpowered track block will stop before reaching the switch. The track block after the switch is constructed so a train will clear before a second train is started through the switch.

The 2RC is jumpered for the Only-One-ON feature set and the "Extended-OFF/ON" feature (for both Relays).

Connections are wired as follows:

• The 2RC is powered with a 12 - 14 volt transformer.
• The isolated outside-rail track blocks are powered with an 8 - 20 volt transformer connected to track common and the "B" terminals of both outside-rail inputs.
• The leading track blocks are connected to Input-1-A and Input-2-A terminals. The trailing track block is connected to both Input-1-A and Input-2-A terminals through combining diodes. Thus:
  • Input-1 is activated whenever a train is in the block connected to Input-1-A OR in the "Trailing Track Block."
  • Input-2 is activated whenever a train is in the block connected to Input-2-A OR in the "Trailing Track Block."
• All track blocks are powered from the same train transformer circuit. The "Trailing Track Block" and the track switch are connected to train power (always powered).
• Track power is connected to the C (Common) terminals of both relays.
  • Power for the Input-1 track block is connected to the NO (Normally Open) terminal for Relay-1.
  • Power for the Input-2 track block is connected to the NO (Normally Open) terminal for Relay-2.

This example controls train movement by turning track center-rail power on or off. The engine's E-Unit, or equivalent, must be set so removing and restoring train power will not change the train's direction.

Need to protect trains at a track switch? You need Three-Rail Innovations' Two Relay Controller.

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