Patent GB-168839-A (GB)
Title: Improved system of submarine communication
IPC: H04B11/00
Filed: 1918-03-26
Abstract: 168,839. Mazza, L. March 17, 1917, [Convention date]. Void [Published under Sect. 91 of the Act]. Subaqueous audible signals; subaqueous transmission of speech; locating subaqueous sounds.- In apparatus for subaqueous sound signalling, transmission of speech, and locating reflecting surfaces by the echo method, an electromagnetic oscillator is used as a transmitter, and microphonic apparatus is used for receiving, vibrations being transmitted between the oscillator proper and its diaphragm, and the microphone and its diaphragm, through a body of liquid the pressure of which can be adjusted either for balancing the external pressure due to submersion or for tuning purposes. Two sets of apparatus are provided, one at each side of the ship, so that by comparison of the received sounds the direction of the source may be estimated. The oscillator (the action of which is reversible so that it may be used for receiving) comprises rings assembled to form a chamber which is closed at one end by a cap 8 and at the other by a diaphragm 1, the whole being connected to the ship's stern by a ring 2 so that the external face of the diaphragm 1 is in contact with the sea water. Two opposed windings 9, 10 housed in recesses within the c.asing are supplied with direct current. An inner cylinder 11 carries a winding 12 supplied with alternating current, either from a suitable generator, the circuit being controlled by a key for code signalling, or from a microphone for speech transmission. A copper cylinder 13 oscillates in the airgap between coils 9, 10 and 12, under the action of induced currents. The cylinder 13 is clamped between perforated end-plates 15, 15<1> and is supported at one end by a perforated diaphragm 18<1> and at the other by a diaphragm 20. The central clamping rod 14 carries a disc 19 acting as a piston working in a cylindrical portion of a ring @4. The spaces 21, 22 at each side of the piston are filled with liquid which extends through valve-controlled tubes 28, 30 and partly fills a reservoir 27. The upper part of reservoir 27 communicates with an air filled reservoir 33, which communicates through a tube 34 with the interior of the air-filled chamber to the right of diaphragm 20. Perforations in plates 15, 15<1>, diaphragm 18' and cylinder 13 provide the necessary through communication to allow the air in the interior of the apparatus to remain at the same pressure as that in reservoir 33. A depending tube 35 from reservoir 33 communicates with the sea, so that pressure adjustment corresponding with depth of submersion is obtained. In a modification, diaphragm 20 and piston 19 are omitted. The plate 15 is arranged to take the place of the piston, and a perforated supporting diaphragm similar to the diaphragm 18<1> is used to the left of the plate 15. In both forms, the central clamping rod 14 may be extended to the left and directly connected to the diaphragm 1. In a further modification, the chamber 21 may be at some distance from the rest of the device and communicate therewith through a tube. It is also stated that the electrical arrangements may take the form of a suction solenoid, and pneumatic, hydraulic, or mechanical operation may be substituted for electrical operation. The receiving apparatus, Fig. 6, comprises a diaphragm 45 in contact with the sea-water and forming a closure to a chamber 52 within which is supported a ring or box 47 closed by diaphragms 48, 48'. The microphone capsule (not shown) is contained in this box. The interior of box 47 communicates with air reservoir 33, and the chamber 52, filled with liquid, communicates with reservoir 27. In a modification, the microphone box 47 is contained in a stout liquid filled casing which can be put into communication with the oscillator chamber for receiving. The effects of local disturbances are minimized bv the use of microphones attached to the hull of the ship and supplying current which acts in opposition to, and so neutralizes, the currents due to the action of the same disturbing causes on the receiver. Various circuit arrangements are described, one of these involving the use of a Wheatstone bridge.