Patent GB-143583-A (GB)
Title: Improvements in or relating to electrical transmission, particularly applicable to radio-telegraphy and telephony
IPC: H04B14/08
Filed: 1918-08-02
Abstract: 143,583. Levy, L. Aug. 4, 1917, [Convention date]. Wireless signalling.-In a continuous-wave signalling system, the high-frequency oscillations are modulated at an ultra-acoustic frequency, either at the transmitting-station, or at the receiving-station, or both, and the receiving-station is provided with circuits tuned to the high-frequency and to the modulating frequency. The invention may be applied to simultaneous telegraphy and telephony, and several modulating frequencies may be employed. The invention may be applied to line-wire transmission and to printing-telegraphs. In the transmitting-arrangement shown in Fig. 1, the grid circuit of a highfrequency generator 1 is coupled to a lower-frequency generator 2 by a transformer 6, 20, and a circuit 6, 7 in this grid circuit is tuned to a circuit 20, 21, 22 in the plate circuit of the generator 2. The grid circuit of the generator 2 is coupled to a circuit containing a microphone 24, when the arrangement is applied to telephony, in order that the oscillations of the generator 2 which are employed to modulate the oscillations of the generator 1 may be modulated by oscillations of speech frequency. In a modification, the high-frequency oscillations of the generator 1 are modified by the lower-frequency oscillations of the generator 2 by supplying these low-frequency oscillations direct to the aerial or plate circuit of the generator 1. In a further modification, a circuit tuned to the frequency of the circuit 20, 21, 22, Fig. 1, is placed between the points X, Z, Fig. 1. Wireless signalling may be performed by varying the frequency of the circuit 20, 21, 22 by short-circuiting some of the turns of the inductances 20 or 21. In the receiving-arrangement shown in Fig. 7, a circuit 29, 30 in the grid circuit of a detector 40 is tuned to the frequency of the generator 1, Fig. 1, and the plate circuit of this detector is coupled to the grid circuit of a second detector 50, this grid circuit containing a circuit 48, 49 tuned to the frequency of the generator 2, Fig. 1. The plate circuit of the detector 50 contains a telephone receiver 57 operated by the modulated current of speech frequency. A filtering-circuit 58, 59, 60, 61, Fig. 8, may be placed in the plate circuit of the detector 40, by means of which low-frequency oscillations are filtered out and supplied to the second detector 50. When applied to wireless telegraphy in which the microphone circuit shown in Fig. 1 is dispensed with, locally-generated oscillations of a frequency approaching the frequency of the oscillations generated by the generator 2, Fig. 1, are supplied to a coil 64, Fig. 7, in order that a beat frequency may be supplied to the telephone receiver 57. When the transmitted waves are not modified at an ultra-acoustic frequency, a local generator is coupled to the circuit 29, 30 through a coil 65, the frequency of this generator being such that it gives ultra-acoustic beats with the received oscillations. Amplifiers may be employed in the receiving-circuit. In the arrangement shown in Fig. 10, a continuous-wave arc system, comprising an arc 70, a generator 75 protected against high tensions of high and low frequencies by condensers 76, 77, induction coils 79, 81, and impulse coils 80, 82, operates in conjunction with a second arc system of lower frequency adapted to effect telegraphy, and a lamp-valve reaction system of a low but different frequency from that of the subsidiary arc to effect telephony. The oscillatory circuit 88, 96 of the subsidiary arc is coupled to a circuit 84, 85 connected across the arc 70, while the tuned circuit 22, 89 of the plate circuit of the reaction generator 90 is coupled to a circuit 86, 87 connected across the arc 70. The plate circuit of the generator 90 is supplied by a condenser 91 connected across the generator 75 through iron-cored coils 92, 93. Compensating- condensers 84, 86 are placed in series with the coils 85, 87 respectively. The oscillations produced by the main arc 70 are modified by the superposed electromotive forces due to the subsidiary arc 97 and the generator 90, and telegraphy and telephony are simultaneously carried on by short-circuiting periodically a portion of coil 88 and by modifying the output of the generator 90 by means of amplified speech currents derived from a battery 25 and a microphone 24. The combined telegraphic and telephonic receiving-apparatus operating in conjunction with the transmitting system shown in Fig. 10 comprises a detector 105, Fig. 11, a detector 106, and a lamp device 107 operating as a detector and as a generator of oscillations. The detector 106 operates in the same manner as the detector 50, Fig. 7, while the lamp device 107 is connected to operate as a detector and a generator of oscillations by connecting a circuit 103, 104, coupled to the coil 100, across the grid 111 and plate 110, and causing the beats between the oscillations received by the circuits 103, 104 and the oscillations generated by the device 107 to operate a telephone 116, these beats ceasing when a portion of the coil 88, Fig. 10, is short-circuited. Telephonic reception occurs in the receiver 119 as in the arrangement shown in Fig. 7. In the arrangement shown in Fig. 12, two coupled high-frequency generators 125, 126 are connected to emitting-aerials 131, 132, and a circuit 29, 30 at the receiving-station, tuned to the ultra-acoustic beat frequency of the generators 125, 126, is coupled to the receiving-aerials 127, 128.