GB1500764A - Transmitter-receiver devices for use in the ear - Google Patents

Abstract

1500764 Two way transmission using earpieces O TANI 31 May 1975 23726/75 Headings H4J and H4R In ear-plug transducer apparatus, the transducer on the one hand converts sound pressures generated by the voice of the wearer and transmitted via the tympanic membrane and the auditory canal to the transducer where they are converted into corresponding audio frequency electrical signals and on the other hand converts audio frequency electrical signals received by the apparatus for acoustic reception by the wearer. Apparatus 1 (Fig. 1) has a hollow body 2 with an end 2a for insertion into the auditory canal 18. A transducer 6, as shown a piezoelectric bimorph, but which may be of crystal or condenser type (not shown), is fixed to a projection 2b and is coupled to a vibratory diaphragm 8. An air hole 12 reduces the mechanical impedance of the vibratory system and co-operates with an air hole 14 on the other side of the diaphragm 8 to reduce or eliminate ambient noise. Instead of providing two holes 12, 14 parts of the hollow body 2 on each side of the diaphragm 8 may be flexible. An electrostatic or electromagnetic shield 16, which may be coating of conductive paint, metal mesh or a metal shield is preferably provided inside the hollow body 2 and is connected to the earth wire of a lead 10 connected to the transducer 6. The apparatus may be used for "hands free" telephone conversation, in transceivers and for underwater communication. In a two party transmission system each party is provided with a transmitting amplifier AMP1 or AMP3 (Fig. 7), a receiving amplifier AMP2 or AMP4, a control circuit CC 1 or CC2 and switches SW1, SW2 or SW3, SW4. In a passive condition in which no sound is picked up the amplifiers AMP 1 and AMP3, the control circuits CC1 and CC2 and the switches SW1 and SW3 are in operative condition whereas the amplifiers AMP2 and AMP4 and switches SW2 and SW4 are in non- operative condition. A voice frequency electrical signal emitted by right hand apparatus 1 actuates the control circuit CC2 of the other apparatus 1 to cut off the transmitting amplifier AMP3 of the other apparatus and to actuate the corresponding receiving amplifier AMP4, thereby conditioning the other apparatus for reception of the voice frequency signal. All the circuit members are returned to the state corresponding to a passive condition upon termination of the voice frequency signal. A voice frequency electrical signal subsequently emitted by left hand apparatus 1 conditions the circuit in an analogous manner.