Patent GB-1252411-A (GB)
IPC: H04B5/00
Filed: 1967-10-25
Abstract: 1,252,411. Deaf aids. A. L. WALKER. 6 Dec., 1968 [25 Oct., 1967; 19 Dec., 1967; 2 Aug., 1968], Nos. 48429/67, 57554/67 and 36904/68. Heading H4J. A personalized hearing aid comprises a closespeaking microphone 28 (Fig. 2) for use by a partially deaf person to hear his own voice. An amplifier and a frequency compensating circuit are both common to the microphone 28 and to a receiver 2, which includes a remote reception circuit (e.g. radio or inductive loop). The frequency compensating circuit co-operates with earphones 27 to suit the audio frequency loss of the deaf person. The microphone 28 and receiver 2 are simultaneously operable and signals from both are subject to similar frequency compensation. A transmitter 1 (Fig. 1) for use by a tutor transmits to the receiver 2. A case 4 of " hipflask " shape utilizes plug-in circuit modules. A transmitter microphone 6 is covered with a grille and feeds an F.M. transmitter module (not shown). A rotary on/off switch 8, a socket 9 for an aerial 10 and an input socket 13 for connection to a tape recorder or radio are provided on the transmitter 1. The radio frequency of the transmitter 1 is controlled by a plug-in crystal which can be changed if a different frequency is required. The receiver 2 has a "hip-flask" case 5 housing an F.M. crystal controlled transistor tuner module 14 (Fig. 3), an A.F. amplifier module 15 and a compensating circuit module 16. One of a number of crystals 17 is selected by a switch 20 in accordance with the radio frequency of the transmitter 1, a coloured button 19 indicating the channel in use. Alternatively, the transmitter 1 may selectively switch the receiver 2 to the correct channel. A combined on/off switch and volume control 22 is provided together with a three-position switch 23, a socket 24 for use with a tape recorder or microphone, and a socket assembly 25 which connects earphones 27 to the output of the frequency compensating circuit 16, boom microphone 28 to the input of amplifier 15 and an aerial (which may be provided by the headset and its downlead) to the tuner module 14. The positions of switch 23 are (1) socket 24 and microphone 28 operative, (2) tuner module 14, socket 24 and microphone 28 operative, (3) tuner module 14 and socket 24 operative. The headset 3 may be replaced by a monaural earpiece fitted to an ear mould, an external microphone being connected to the socket 24 and mounted on a lapel or clipped on to a pocket. Six frequency characteristics are given for the frequency compensating circuit, together with a flat response (Fig. 4, not shown). When hearing loss is total in one ear the frequency compensating circuit compensates for loss in the other ear. When the ears have different audiograms two separate compensating circuits are provided, one for each ear, or different earphones may co-operate with a single compensating circuit. The two earphones may be energized at different volume levels. The earphones may each have two transducers, responsive to high and low frequencies respectively. The compensating circuit module 16 may be replaced by tone controls. Several people may be provided with identical transmitters. Where an inductive loop is provided, this may be supplied by a radio frequency loop.