Abstract: An automatic car carried departure test unit including an integrated circuit code oscillator for generating coded signals and an integrated circuit carrier oscillator for producing a carrier signal which is modulated by the coded signal to produce coded carrier signals. The coded carrier signals drive a current source which directly injects current signals into a pair of series aiding pick-up coils for testing the reception of coded speed command signals by the pick-up coils and the amplifier of the cab signal receiver. An integrated circuit speed oscillator produces simulated speed signals which are logically processed in sequential order to verify the operation of the overspeed functions of the automatic train protection equipment.

Abstract: A transistorized power supply for providing a constant voltage to a load. A series regulator interposed between a d.c. input voltage source and the load to regulate the d.c. output voltage. A d.c. to d.c. converter serially connected between the d.c. input voltage source and the series regulator. The d.c. to d.c. converter is selectively actuated to supplement the d.c. input voltage when the d.c. input voltage falls below a predetermined value in order to maintain a constant voltage across the load.