GB763194A - Improvements in or relating to the relaying of television pictures over wires - Google Patents

Abstract

763,194. Distributing music &c. BRITISH RELAY WIRELESS, Ltd., RUSSELL, K. A., and MACDONALD, D. A. May 25, 1954 [June 3, 1953], No. 15328/53. Class 40 (4). In a wired television relay system two screened cables are provided, each having two or more pairs over which video and audio signals are transmitted, and a sinusoidal signal, which provides line-scanning power, is transmitted over a phantom circuit using some or all of the conductors of each cable. As described, each of the cables 10, 11 has two pairs of conductors over each of which the video and audio signals pertaining to a separate television programme are transmitted. The four conductors (e.g. 12-15) are laid up as a quad around a central unpaired conductor (e.g. 16) and the whole is surrounded by a screen (e.g. 17) The combined vision and audio signals for the four television channels are applied to windings 30-33 of the four input transformers. The vision signals are in the form of amplitude modulation on a high-frequency carrier for example of 3.5 Mc/s. The frame scan waveform is applied to winding 50 and hence is transmitted over a circuit formed by the two central conductors 16 and 22 balanced about the screens of the two cables. The sinusoidal line scan power is obtained from generator 55 and is transmitted over a phantom circuit formed by the screens and the five conductors of each cable. This circuit effectively has conductors of larger section than the paths for the frame scan, vision and audio signals, which is desirable since the line scan power is substantially larger than that transmitted over any of the other paths. At each receiver the ganged contact arms 64, 69 serve to select the desired programme. The frame scan signals are applied to the two halves 80, 81 of a split time-base deflection coil, connected respectively between the centre conductors 16, 22 and the screens 17, 23. The two screens are also coupled through condensers 82, 83 to transformer 85 from which line defection power and E.H.T. voltage may be obtained as described in Specification 763,193. This power can be taken from the phantom circuit by coupling to the screens only since there is a large capacity between them and the conductors.