GB1334183A - Headset - Google Patents

Abstract

1334183 Piezoelectric microphones; headsets STANDARD TELEPHONES & CABLES Ltd 21 Oct 1971 48953/71 Heading H4J A headset (Fig. 1) comprises a housing 10 containing an insert earphone 21 (Fig. 2) having an earpiece 11 for insertion in a user's ear, a microphone 13 carried at the end of a boom 12 formed from a piece of plastics tube, and a head pad 42 attached to the housing 10 by an underthe-chin bond 15. The upper end of the microphone boom has an enlarged portion 18 which slides both longitudinally and rotationally in a recess in the housing, the rotational movement being limited to 150 degrees to prevent lead damage. When longitudinal movement of the boom occurs the microphone lead is pushed into or pulled out of a cylindrical cavity 24 contained in the housing. The microphone (Fig. 7) is of the type disclosed in Specification 1,278,009 in which a piezo electric transducer is mounted by a rubber or other flexible sealing ring mid way along a cylindrical housing. The two part housing is closed at both ends, 314, 324 and holes 316, 325 are provided for the ingress of sound. The cavities formed between the transducer and the cylinder ends are arranged to be acoustic resonators at a predetermined frequency e.g. 4 KHz. and are said to provide an upper frequency limit to the microphone output. The cavities may have an open celled foam, e.g. polyurethane contained therein behind the apertures 316, 325. A preamplifier 26 is provided in the housing 10 for the microphone. The insert earphone 21 is a magnetic diaphragm electro-acoustic transducer of the miniature "button" type without its back cover which is held in the housing by a ring 23 and with a disc (not shown) behind it. Alternatively a complete earphone with its back cover may be used. The housing is in two parts 16, 17 to allow for the insertion of the components. The earphone may be inserted from the open end of cavity 22 and be held in place by a bent over lip. The housing has a further cavity 27 in which terminal pins may be housed to enable the connections between a five core cable 14 and the various components to be effected. The head pad 42 may be replaced by a second earpiece 11 and holes may be bored through the mounting 40 to enable the user to hear external sounds. Alternatively a second earphone may be provided, the leads to it being carried from the housing 10 inside the under-the-chin band 15. Specification 1,278,009 is referred to.