GB379305A - Wireless system - Google Patents

Abstract

379,305. Wireless signalling. BRUNI, R., 36, Via XX Settembre, Genoa, Italy. March 20, 1931, No. 8583. Convention date, March 20, 1930. [Class 40 (v).] In a wireless signalling system of the kind in which the carrier wave is modulated by audio-frequency-modulated currents of intermediate frequency while at the receiver a local oscillator is provided between the first and second stages of detection, the local frequency beats with the auxiliary frequency while disturbances produce beats of different frequency which are not passed on to the next stage. Fig. 13 shows the transmitting arrangement in which currents from the microphone 1 are amplified at 6 and modulate the intermediate frequency generated by the valve 27 through the coil 12, which varies the constants of the tuned circuit 21, 19<1>. The carrier current generated by valve 28 is modulated by the resultant current in the anode circuit of valve 27 by choke modulation at 13<1>. At the receiver, Fig. 14, the input is applied to a first detector comprising two valves 511, 51<11>, in parallel, their anode circuits being arranged in pushpull in order to balance out disturbing currents. Local oscillations from valve 59 are injected into the circuit by coupling coil 58 to the circuit 68, 69, the frequencies being so chosen that the signal beat frequency differs considerably from that due to disturbing currents. The beat frequency is transferred to the second detector 72 from circuit 56, 57. High frequency amplifiers may be provided before the first detector stage 51<1>, 51<11> and intermediate frequency amplifiers between the two detection stages ; also the local frequency may be obtained by a second grid in the valve 51<1>, Fig. 15 (not shown). The valves 51<1>, 51<11>, may be,combined in one envelope and a second grid may also be added to the valve 51<11> to obtain symmetry, Figs. 16, 17, and 18 (not shown). Specifications 143,583, 158,200, 219,998, 314,092, [all in Class 40 (v), Wireless signalling &c.], and 341,832 are referred to.