Abstract: An audio current pick-up device for use with an electric wire 6 carrying an electric current containing audio information comprises a pair of substantially identical magnetic induction coil assemblies 26, 27 disposed in parallel to each other with an axial deviation and orthogonally to the wire, each coil means including a magnetic core in the form of rod 30, 38 and a pair of induction coils 32A, 32B, 39A, 39B wound in opposite directions on respective halves of its core rod. An output of either of the induction coils is phase-shifted by a preset amount and composited with an output of the other magnetic induction coil to form a sound pick-up signal from which a sound output signal is derived.

Abstract: The invention relates to an electromagnetic induction coil or antenna device embedded in hearing aids or radio sets for receiving sound signals or carrier signals generated by a primary electromagnetic induction coil which is laid down in the room. A plurality of coils each one end of which is commonly connected and each other end of which extends outwardly from the one end so as to be uniformly arranged in a space and a phase selector connected to the coils operates, as a mercury switch, to pick up positive phase component output signals which are induced in at least any of the coils. The coils and the phase selector are fixedly built in the body of a hearing aid, etc. so that the corresponding coil and conduit in which a suitable quantity of mercury is charged may be paralleled to each other and so on, thereby to obtain a constant output sound pressure irrespective of the posture of a person wearing a hearing aid or enjoying television.

Abstract: A hearing aid appliance has induction loops which are magnetically coupled to hearing aids held individually by hard-of-hearing persons. The number of induction loops is an integral multiple of two, and each induction loop is in the form of a rectangle having at least two parallel sides. The parallel sides of the induction loops are arranged in parallel with one another and equally spaced from one another so that signal currents flowing in adjacent parallel sides are shifted by 90.degree. in phase.

Abstract: A sensing coil unit for a hearing aid is made up of a sensing coil which is in the form of a cylinder one end of which is heavier than the other end and is floated in the liquid in a sealed container, so that the sensing coil is vertical at all times irrespective of the positions of the hearing aid thereby to maintain constant its magnetic coupling condition with the inductance coil which is laid to transmit voice signals to the sensing coil.