GB408221A - Improvements in or relating to telephone transmitters for use in telephoning, public address systems, and sound recording - Google Patents

Abstract

408,221. Transmitters. STEUART, D. S. S., and STEUART, M. S., St. Mark's House, St. Mark's Square, Regent's Park, London. Oct. 3, 1932, Nos. 27460/32 and 22694/33. [Class 40 (iv).] A transmitter 2, Fig. 9, for use in telephone, public address and sound recording systems and the like comprises a pair of diaphragms 3, 4 responsive to different audio frequency ranges, e.g. constructed of different forms of carbon and arranged to act on a common mass of granules 2<a>. The transmitter is mounted in a coneshaped member 7 which is itself mounted by means of a tube 27 and nuts 29, 31 in a bellshaped mouthpiece 1, the member 7 being filled with sound absorbent material, such as cork granules, and formed with reflecting surfaces 5, 6 arranged so that equal portions of oncoming sound waves are caused to impinge on the diaphragms 3, 4 simultaneously. If desired, an additional sound reflector may be provided between the surfaces 5, 6. Fig. 6 shows a modification employing a slightly different form of transmitter 15 and in which the mouthpiece is divided into two separate sound passages 13, 13<a> having flat reflecting surfaces 14, 14<a> at their inner ends and united at their outer ends by a common partition 11. According to a further modification, Fig. 8, three duplex diaphragm transmitters 22 are arranged in a common housing 24 having protective wire gauze covers 23 whilst in a still further modification, Fig. 3, two transmitters 8, 9 are employed electrically connected at 10, bell-shaped mouthpieces 8<c>, 8<d> and sound passages 8<a>, 8<b> leading to opposite sides of the transmitter 8 whilst similar mouthpieces 9<c>, 9<d> and passages 9<a>, 9<b> lead to opposite sides of the transmitter 9.