GB1058129A - Improvements in or relating to matrix circuit arrangements - Google Patents

Abstract

1,058,129. Colour television. MULLARD Ltd. Nov. 6, 1963, No. 43802/63. Heading H4F. [Also in Division G4] To obtain the G-Y colour-difference signal by combining the R-Y and B-Y colourdifference signals, a colour television matrix arrangement as shown in Fig. 4 is used wherein the signals - (R-Y), - (B-Y) and a D.C. bias are applied to terminals 1, 2 and 8 respectively and by selecting appropriate feedback resistors R 9 and R 10 the G-Y signal is obtained at the terminal 4 which is connected to a variable tap on anode resistor VR 8 , the R-Y and B-Y signals also being obtained at terminals 3 and 5 which are connected to variable taps on anode resistors VR 7 and VR 9 , respectively. Because the circuit is cathode-coupled it does not produce a coloured hum-bar and it has a good highfrequency response, and in addition the circuit is not very susceptible to variations in circuit components. By inclusion of a cross-talk resistor R 12 the cross-talk is reduced between terminals 3 and 5 from 5% to 1%. To substantially remove cross-talk, cancellation resistors R 13 , R 14 and R 15 are connected as shown in Fig. 5 and their values are selected to satisfy certain conditions (see Specification). Resistor R 14 may be connected to the zero potential terminal 7 instead of the anode supply terminal 6 and in this case one or more blocking capacitors are included in series with the cancellation resistors to prevent any direct current drain from terminal 6 to terminal 7. The Specification includes values of the circuit components shown in Figs. 4 and 5 and states that transistors may be used instead of thermionic valves.