Patent GB-567334-A (GB)
Title: Improvements in or relating to emergency transmitters
IPC: H04B1/034
Filed: 1943-08-06
Abstract: 567,334. Signalling by visible signals. BENDIX AVIATION CORPORATION. Aug. 6, 1943, No. 12757. Convention date, July 10, 1942. [Class 118 (ii)] [Also in Group XL] A transmitter is enclosed in a buoyant waterproof case and comprises a manually driven power source, a radio transmitting circuit and a light circuit energizable from the power source, means for impressing signals on the radio circuit and light circuit, and means for selecting either the radio circuit or the light circuit for transmitting. As shown in Fig. 1, the apparatus is enclosed in a casing 10 of drawn aluminium which is closed at the front by a plate 22 secured in waterproof manner with the inter-position of a rubber gasket. The casing is shaped so as to fit between the legs of an operator, Fig. 11, to which it may be fixed by webbing straps 74. An aerial wire 36, supported by a kite or a balloon is connected to the end of a cord 33 for winding on a reel 28 having a folding handle 30. The reel 28 is carried on a door 26 which, when the aerial is wound in, is turned to close a recess 24 in which the reel 28 is stored. An aerial lead 32 can be clipped at 35 to the aerial and enters the casing through a watertight gland 34. A plug 40 has connected to it an earth lead and can be unscrewed and dropped into the sea from a raft or on to damp earth to provide an earth connection. A detachable crank handle 16 engages through ratchet mechanism with a shaft which passes through the casing in waterproof manner, and serves to drive an electric generator which supplies energy for the radio transmitter and also for a signalling lamp 86, Fig. 11, adapted to be connected to socket terminals 50, Fig. 1. The crank shaft also drives through a friction clutch and gearing a set of rotary cams for giving predetermined calling and distress signals either on the radio or on the signalling lamp a centrifugal brake limiting the speed of rotation. A selector switch 46 enables an operator to select firstly whether the signal shall be given on the radio or on the lamp, and then to select a choice of automatic signals, or to enable a signal to be given manually by means of a push-button 44. The operator turns the crank 16 to a sufficient speed as shown by a light 20 and then tunes the radio transmitter by a knob 48 to give maximum brightness of a neon light 18 connected in the aerial circuit. The electrical circuits are shown in Fig. 14 which shows crank 16 driving both the generator 56 and the automatic signal cam mechanism 159. Selector switch 46 connects to ground either signalling lamp 50 or the cathodes of the transmitter valves 210, 212 and selects the signal to be sent. The transmitter circuit comprises the aerial 278 fed from a highfrequency oscillator 212 having the screen grid back-coupled to the tuned grid circuit, and having its grid modulated by the output of an audio frequency oscillator 210 fed through condenser C3 and audio-frequency choke 262. The audio oscillator comprises a double triode VI, V2 with a common cathode 236 and cathode resister R3. The anode of V1 is coupled through resister C1 to the grid of V2, while the anode of V2 is coupled to grid of V1 through the common cathode resister. The gain of V1 is made greater than that of V2 by making R6 greater than R5. Thus the differential effect of regeneration in R3 results in oscillation, the period being determined by the condenser C1 and the resistances R2-R6.