What transformer do you intend to use?
Do you want the light on all the time?
Do you intend to trigger it with contactors or with insulated rails?
From memory, terminal #1 is the common connection, #2 is the lamp, and #3 is the solenoid (electro-magnet that makes the dispatchers move.)
Here's one (of several) solutions:
Assuming you want to use insulated rails, put steady hot (14 Volts) on #1, ground (same as track return) on #2. That will give you a steady lamp in the tower.
Run a wire from any (both) insulated rails to terminal #3. The solenoid has hot on one side, waiting for a ground to complete the circuit. When a train passes over an insulated rail, the solenoid will operate.
