Inductive coupling for aircrew helmet microphones and earphones - has coil coupling via twin loops in seat headrest and similar loops in back of helmet

摘要

The inductive coupling is for helmets as used by aircrew allowing the user freedom of movement without the danger of pulling out or damaging connection jacks used in wire coupling. The coupling is via twin loops in the users seat headrest and similar loops in the back of the helmet. The pair of coils (18, 19, and 16, 17) are associated uniquely with the microphone and earphone circuits and are interconnected by a duplexor (131). Power for the helmet circuits is supplied from rechargeable batteries (43) charged from a full-wave rectifier (28) and smoothing circuit (45, 46) connected across one pickup coil (16) which is shunted by a capacitor(25). The microphone (12) and earphones (11) have separate amplifiers (58, 64, 68), the former a modulated oscillator (67) and the latter a frequency discriminator (56).