Patent GB-753313-A (GB)
Title: Improvements in or relating to colour television systems
Inventor: JESTY LESLIE CONNOCK
IPC: H04N11/00
Filed: 1953-07-16
Abstract: 753,313. Television. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. June 17, 1954 [July 16. 1953], No. 10474/53. Class 40 (3). In a colour television system high definition green signals are added to low definition signals in all colour channels. This arrangement causes the high-definition green information, which carries the fine black/white detail, to be reproduced in monochrome which is stated to produce a more pleasing effect than if reproduced in green and to reduce the stringency of colour registration otherwise required for the reproduction of good definition colour pictures. Fig. 1 shows one embodiment in which the output signals from the " green camera GP, occupying a frequency range o-f2, are split into a high-frequency portion f1-f2 and a lowfrequency portion o-f1 by means of filters HDG and LPFG respectively, the output of the former being fed after amplification in HDGA to an adding circuit AG in which it is combined with the output of the latter and to further adding circuits AR and AB in which it is combined with the o-f1 range of the signals .supplied by the red and blue " cameras RP and BP respectively. The outputs of the adding circuits are then transmitted by radio or cable to the picture reproducing devices CRG, CRR and CRB for the green, red and blue component images respectively. In a second embodiment (Fig. 2) the " green " camera GP supplies a signal in the range o-f3 which is split into three ranges o-f1 ; f1-f2 ; f2-f3 by means of filters LPFG, MDG and HDG, respectively, the output of the latter, after amplification in HDGA<SP>1</SP> being combined in adding circuit AG with the output of the other two filters and supplied to the " green " transmission channel. The " red " and " blue " cameras RP and BP supply signals in the ranges o-f2 and o-f1 respectively, the former being split into ranges #1-#2 and o-#1 by means of filters MDR and LPFR, the outputs of both of which are combined with the output of HDGA<SP>1</SP> in adding circuit AR and supplied to the " red " transmission channel and the output of the " blue " camera BP being combined in adding circuit AB (connected in the " blue " transmission channel) with the output of HDGA<SP>1</SP> and with the outputs of MDG and MDR after attenuation in AMDG and AMDR respectively. In a third embodiment (Fig. 3) the output of the " green " camera is split into ranges o-f1 and f1-f2 and the latter range, after amplification in HDGA, is combined with the former and with the outputs of the " red " and " blue " cameras in adding circuit AGRB. The output of this latter circuit provides the " green transmission channel comprising a monochrome component in the range o-f1 and a " green " component in the range f1-f2. The former component is separated out by means of a filter BMF and combined subtractively in circuits STR and STB with the " red " and " blue " camera output signals respectively to provide two further output channels in the range o-f comprising, respectively, signals of the " red minus monochrome " and " blue minus monochrome " type.