GB479935A - Improvements in or relating to methods of producing electrical oscillations - Google Patents

Abstract

479,935. Valve generating circuits. BAIRD TELEVISION, Ltd., JOHNSTONE, D. M., and JONES, V. July 13, 1936, Nos. 19355 and 27286. [Class 40 (v)] A frequency-divider is so constructed as to produce a definite phase relation between the original current of basic frequency and the derived current of submultiple frequency. To this end the original impulses from the source are applied to a transmission channel and also to a known frequency-divider, the output of which is used to switch the transmission channel on and off so that some impulses coming from the source are suppressed while others are transmitted so as to form a sequence of impulses at the submultiple frequency, Fig. 1 (not shown). In the arrangement shown in Fig. 2, the original current is applied to the grid of valve 8 and the submultiple current is taken off the anode circuit at 12. Alternate impulses are suppressed by switching-impulses derived from the valve 10, which is controlled through a delay network 9. The switching-impulses may, however, be made long enough to suppress a larger proportion of impulses so that the frequency may be divided by a factor greater than 2. In the switching-device shown in Fig. 3, the valve 14 is back-coupled so that it is capable of oscillating when condenser 15 has been charged to a sufficient potential through the resistance or constant-current device 16, whereupon the condenser 15 is discharged through the valve 14. The original impulses consist of trains of high-frequency oscillations applied to the screening grid at 21, but alternate impulses, or some other proportion of impulses, are suppressed by the condenser potential not having acquired a sufficient value. The potential of condenser 15 is applied through a differentiating circuit 19, 20 to a valve 10. This valve switches a transmission device to which also the source impulses are applied. The transmission device may comprise a fourelectrode valve in which the switching-impulses are applied to the screen grid while the original impulses are applied to the control grid, Fig. 1, Provisional (not shown). Where the original impulses are television synchronizing signals, the derived impulses may be mixed with impulses derived from the A.C. mains and employed for control purposes as described in Specification. 472,686, [Group XXXV]. In a further modification, the transmitted impulses may be derived by submultiplication from impulses which have themselves been derived by multiplication from the switching-impulses.