21 CHOPPERS, VIBRATORS, POWER SUPPLIES, CHOKES, INVERTERS, RELAYS, CIRCUIT BREAKERS, MAGNETIC AMPLIFIER, AND MARINE LIGHTING CONVERTERS
FIRST USE JUNE 1, 1946, ON VIBRATOR POWER SUPPLIES; IN COMMERCE OCT. 1, 1946. FIRST USE JUNE 1, 1946, ON VIBRATOR POWER SUPPLIES; IN COMMERCE OCT. 1, 1946.