GB191322157A - Improvements in or relating to Telephone Transmitting Apparatus. - Google Patents

Abstract

22,157. Foote, A. H. Oct. 1. Telephones, mounting and supporting.-Microphones are mounted with their diaphragms in parallel planes, and so that the axis of the sound waves is normal to the line joining the microphones. A handle C, Fig. 1, bears a bracket B carrying two microphones A, the position of which can be adjusted laterally by means of thumb-screws A<2> on bolts which pass through slots in the bracket B. Microphones.-The microphones may be differential, and of the design shown in Fig. 3. Two plates A<6>, A<21>, perforated with holes A<7>, A<22>, have clamped at their centres the plates A<10>, A<25>, bearing the electrodes A<9>, A<24>. Between them, and suitably insulated from them, is clamped the diaphragm A<13> in such a way as to leave flat annular spaces A<12>, A<28> from which the granules are excluded by fluffy asbestos or similar packing A<29>. The parts are fastened together by bolts A<30> which engage the interior screw-threads of larger bolts A<32> so as to hold the back-plate A<5> in position. A conical sound-reflector A<11> is provided. The terminal A<18> is in electrical connexion with the diaphragm by way of a ring of metal A<17> which is insulated by a ring from the plate A<21>. To avoid packing, the quantities of granuies on either side of the diaphragm are equal. Telephone systems.-The arrangement of the circuits is shown in Fig. 6, wherein A<13> are the central or vibrating electrodes (i.e. the diaphragms) and A<9>, A<24> are the fixed electrodes of two microphones connected in multiple arc, and in series with a source of current G and resistance L. The diaphragms A<13> are connected to the line-wires L<1>, in which condensers L<2> &c. may be placed.