GB394711A - Improvements in or relating to television and like facsimile signalling systems - Google Patents

Abstract

394,711. Television; synchronous movements. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, and PLAISTOWE, D. L., 21, Oakleigh Park Drive, Leigh-on- Sea. Jan. 1, 1932, No. 92. [Class 40 (iii).] In a system utilizing synchronizing impulses of greater amplitude than the picture signals, the separation of the synchronizing impulses at the receiver is effected by applying the signal input to an arrangement including a glow-discharge tube, across the electrodes of which is applied a constant D.C. voltage, lower than the ignition voltage, and of such a value that the high-amplitude impulses cause the tube to break down and to pass current which is utilized to produce impulses which are applied to the synchronizing winding of the receiver motor. The synchronizing impulses, derived from a master frequency device such as an electrically-maintained tuning fork, are applied through a transformer 4 to the synchronizing winding 3 of the transmitter motor and to the input circuit of a valve 8 in the plate circuit of which is a neon tube 11 which is arranged to pass current when the voltage applied to the grid of the valve 8 approaches its maximum negative value. These impulses are applied through a transformer 12, 15 to an amplifying valve 19, the output of which is fed in parallel with the amplified television or picture-telegraph signals to the transmission line. At the receiving end, Fig. 2, the combined television and synchronizing impulses are fed in parallel to the neon tube 26 reproducing the picture, and to a valve 27, in the output circuit of which is a neon tube 31 arranged to pass current when synchronizing impulses are received, the impulses being passed by a transformer 33, 35 to a valve 39 having. in its plate curcuit the synchronizing winding 3<1> of the receiver motor. In an alternative transmitter arrangement, Fig. 3 (not shown) the neon tube 11 is in a circuit transformer-coupled to the valve 8 to which the synchronizing impulses are applied.. In further modifications, Figs 4 and 5 (not shown), the neon tube 11 is in series with the primary winding of a transformer in the output circuit of the valve 8, or is in the output of the valve 8 and is series-connected with a resistance from which the synchronizing impulses are applied to the valve 19.