WITH THIS LIONEL 944 OPERATING SEMAPHORE, PASSING TRAINS AUTOMATICALLY CHANGE THE SIGNAL FROM GREEN TO RED WITH THE USE O THE 153C CONTRACTOR (INCLUDED). IT OPERATES BETWEEN 12-14 VOLTS ALTERNATING CURRENT. THE WEIGHT OF THE PASSING TRAINWITH THE CONTRACTOR BENEATH THE TRACK, BREAKS THE CONTACT WITH GREEN LIGHT AND RED LIGHT WILL STAY ON UNTIL TRAIN PASSES. SIMPLE INSTALLATION DIRECTIONS & ALL CLIPS & CONNECTORS INCLUDED. AGES 8 TO ADULT. NEW IN BOX.