GB1099344A - Personal listening apparatus - Google Patents

Abstract

1,099,344. Personal listening apparatus; inductive signalling. A. FRANKS. Sept. 23, 1965 [Sept. 24, 1964], No. 39036/64. Headings H4J and H4U. Personal listening apparatus comprises physi cally separate and unconnected detector and earpiece sections 10, 30 both adapted to be worn by the user, the detector section 10 comprising a sound detector 16 in the input of an amplifier 18 arranged to drive a transmitting coil 28, and the earpiece section 30 including a coil 36 arranged, when appropriately located in the field of the transmitting coil 28 without being physically connected to the detector section 10, to provide both the energy and intelligence for actuating the earpiece section 30 to yield an amplified version of sound picked up by the sound detector 16. The earpiece section 30 fits inconspicuously within the ear. The transmissions may be at audio frequency or at radio frequency. Preferably the detector section 10 includes a pulse generator 12 which delivers square waveform pulses to a Miller. integrator 14. Variable pulses are applied to a squaring network 20. The output of an oscillator 22 forms, with an amplifier 24, a low power output stage feeding a low impedance system 26. The coil 28 may be attached to a shoulder pad or worn around the neck, e.g. in a tie. The earpiece section 30 consists of an earphone coil 32 and a detector circuit comprising a tuned circuit 34, a detector diode 36 and a clamping diode 38. The coil 32 may itself act as the receiver coil. Two earpieces may receive the same signal, differently attenuated. A stereophonic arrangement may be used in which two input microphones are used to modulate respectively the leading and trailing edges of the transmitted pulses and the two signals are separated in the receiver by reversal of the polarity of the diodes 38 between the two earpieces.