GB279807A - Improvements in or connected with microphones, loud speakers, and the like - Google Patents

Abstract

279,807. De Forest Phonofilms, Ltd., (Assignees of Forest, L. de). Oct. 29, 1926, [Convention date]. Electrocapillary instruments; 7oud-speak-ers.- The diaphragm of an electrocapillary microphone or loud-speaker for sound recording or reproducing consists of the surfaces of a plurality of liquid columns in capillaries formed by juxtapositioned plates placed in a containing vessel. In the construction, Fig. 2, a number of plates 25, each having a communicating hole therein, are provided in an insulating casing 20 so as to form a number of contact surfaces between the dissimilar liquids 22, 23, such as mercury and dilute acid. A thin film of oil may be provided on top of the acid. Terminals 26, 27 contact with the acid and mercury respectively and a horn 21 is connected to the casing 20. A ccnstant potential maintained across the contact surfaces between the liquids is varied in accordance with sound waves directed into the horn 21, whilst conversely, a varying potential across the contact surfaces of the liquids causes movement thereof and produces sound waves Fig. 4 shows a modified construction in which an adjustable thumb screw 33 carries a length of fine wire 34 which contacts lightly with the acid, the screw being connected to one terminal of the primary 39 of a transformer. The other end of the primary 39 is connected as shown with a movable contact, 37 co-operating with a resistance 36 connected across a battery 38 and with the terminal 35 in contact with the mercury. The Specification as open to inspection under Sect. 91 (3) (a) comprises also a construction, Fig. 1, (Cancelled), consisting of a capillary tube 1 closed at one end with a small bulb 2 and diverging upwardly at the other end into a conical horn 3. Terminals 6, 7, in contact with the dissimilar liquids 5, 4 respectively are connected up in circuit as shown, the secondary 9 of the transformer being connected to any suitable input or output circuit according to whether the device is to be used as a loud-speaker or microphone. Fig. 2 (Cancelled) shows a somewhat similar arrangement in which the tube 1 has an open end 2 and the device is connected up in a modified circuit so as to be used as a microphone, the leads 19, 19' from the three electrode tube 18 providing an output circuit. This subjectmatter does not appear in the Specification as accepted.