"Stall-motor" mechanisms for operating track switches, typically, don't come with any control device. The layout builder must provide for basic controls and the non-derailing function. The stall-motor mechanism is usually slow to completely operate the switch, so any non-derailing function must be activated well before the train reaches the switch.

Three-Rail Innovations' Two Relay Controller is connected to provide pushbutton operator action and non-derailing for a stall motor switch machine.

Connections are wired as follows:

• The 2RC is powered with a 12 - 14 volt transformer.
• All track blocks are powered from the same train/center rail transformer circuit.
• The isolated outside-rail track blocks are powered from track center- rail power connected to the "B" terminals of both outside-rail inputs. (The inputs can also be powered with a separate, outside-rail, transformer, 8 - 20 volts.)
• The isolated outside-rail track blocks are connected to Input-1-A (curved) and Input-2-A (straight) terminals through "combining" diodes.
• Electrical push-buttons are also connected, through combining diodes, to Input-1-A and Input-2-A terminals.

The documentation for stall-motor switch machines describes a number of powering and wiring techniques. This example shows a powering transformer (voltage suitable for the mechanism) with two diodes arranged to provide half-wave positive and negative power, through one relay on the 2RC. Wiring determines the direction of movement of the switch machine; arrange the connections to the relay NO (Normally Open) and NC (Normally Closed) terminals so the switch machine sets the switch for "curved" when the push-button connected to Input-1 is closed. Alternately press the pushbuttons to verify that the switch machine moves the switch points to the correct position.

Five jumpers are installed configuring the 2RC for the "Only-One- ON" feature set, "Latched" feature.

Relay-1 and Relay-2 are jumpered to operate in DPDT mode (both relays ON when the Input-2 (straight route) is active. Relays are OFF for the "curved" (Input-1 connected) route. Relays are ON for the straight (Input-2 connected) route.

A train in isolated outside-rail track block "C" will move the switch for the "curved" route. A train in isolated outside-rail track block "S" will move the switch for the "straight" route. The switch motor is always powered and set for the last route traversed.

Activating the "C" pushbutton will move the switch for the "curved" route. Activating the "S" pushbutton will move the switch for the "straight" route. Pushbuttons will not operate when a train is in the isolated outside-rail track blocks.

The "combining diodes" aren't strictly needed for this example, but allow the isolated outside-rail track blocks to be also used for other features, say a block signal. Multiple push buttons can also be connected to operate the track switches from more than one location or to implement multiple track switch routing.

Only one relay is used; the other can be used to power track switch rails, panel indicators, or trackside accessories.

The switch motor can be powered with full-wave DC or a DC power supply using both relays.

Need operator control and non-derailing for your stall-motor switch machines? You need Three-Rail Innovations' Two Relay Controller.

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