21 [ AUDIO FREQUENCY AMPLIFIERS COMPRISING ASSEMBLED UNITS FOR AMPLIFYING ELECTRIC SIGNALS, AUDIOFREQUENCY TRANSFORMERS, CHOKE COILS, ELECTRIC PICK-UP TONE ARMS, ELECTRIC PICK-UP VOLTAGE CONTROLS, ELECTRICAL SOCKETS AND PLUGS, ELECTRICAL PHONOGRAPH PICK-UPS, POWER TRANSFORMERS, ] HIGH VOLTAGE IGNITION TRANSFORMERS [ , AND ENERGIZING TRANSFORMERS FOR ELECTRIC SIGNS ]