GB402291A - A method of synchronising television receiving apparatus by the transmitter - Google Patents

Abstract

402,291. Television. RADIOAKT.- GES. D. S. LOEWE, 10, Wiesenweg, Steglitz, and SCHLESINGER, K., 39, Friedrichstrasse, Friedrichshagen, both in Berlin. March 6, 1933, No. 6685. Convention date, March 7, 1932. [Classes 40 (iii) and 40 (v).] The frequency of a synchronising-signal is a whole-number fraction of the line frequency and an integral multiple of the picture frequency. The synchronising-frequency is in a part of the frequency spectrum little used by the picture signals, and is equal to ##2À#b, where f2 is the line frequency and fb the picture frequency. The synchronising-signal has an amplitude greater than the maximum picture signal, and is separated from the picture signals at the receiver by a tuned filter, Fig. 1 (not shown). The synchronising-signal is reduced to the picture frequency, Fig. 3, and multiplied to the line frequency, Fig. 4, by circuits generating relaxation oscillations. The frequency reduction from 2500 cycles to 25 cycles is performed in a plurality of stages 29-32 reducing respectively by one fourth, one fifth, and one fifth. The condensers 33, 36 of the first and last stages are charged at a constant rate through screengrid valves 11, 12. All the stages are fed from a common charging source, and are coupled by transformers 15, 16, 17. The frequencymultiplying circuit contains a neon tube 10, in the discharge circuit of which is an undamped circuit 19 tuned to the desired harmonic.