A layout has a track crossover that can have a train approach from either leg. Engineers are occasionally distracted, and trains approaching the crossover collide.

Three-Rail Innovations' Two Relay Controller can be connected to control track power in isolated center-rail track blocks leading to the crossover so only one train can traverse the crossover track section at a time.

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

Train direction is as shown. A single train entering either crossover leg will activate the relay controlling power to the leg and be passed over the crossover. 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 crossover, track power is off and the second train coasts to a stop before reaching the crossover. After the first train clears the "Trailing Track Block" the second train is powered and moves through the crossover.

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

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

Connections are wired as follows:

• The 2RC controller 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 and trailing isolated outside-rail track blocks of each route over the crossover are connected to Input-1-A and Input-2-A terminals. Combining diodes from leading and trailing blocks can be employed if either track block is to be used separately for another function.
• All track blocks are powered from the same train transformer circuit. The "Trailing Track Blocks" and the crossover are connected to train power (always powered).
• Track/train center rail 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.

The example uses the same transformer circuit to power both legs of the crossover to accommodate crossovers that have the center rails of both track legs tied together. To use separate transformer circuits either separate the center-rails of each crossover leg or completely isolate the center rails of the crossover and use another 2RC to apply appropriate transformer power.

Trains in either direction over one or both crossover legs can be accommodated by extending the "Trailing Track Block" to be longer than "coasting distance" and connecting center rail power through the relay for the crossover leg.

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.

Trains colliding at a track crossover? You need Three-Rail Innovations' Two Relay Controller.

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