GB698678A - Improvements in or relating to apparatus for use with cathode ray tubes - Google Patents

Abstract

698,678. Television receivers. GENERAL ELECTRIC CO., Ltd., and BRABHAM, H. B. S. June 7, 1951 [June 7, 1950], No. 14222/50. Class 40 (iii). In a television receiver employing a cathoderay tube, the picture signal, which may contain some distortion, is applied to one intensitymodulating electrode of the tube and a second signal, which contains the same general information as the picture signal and is derived therefrom, in a suitably modified form, is applied to another intensity-modulating electrode of the tube, whereby distortion originally present may be subjectively reduced in effect. In the arrangement illustrated in Fig. 1, whereby sharp edges which have been lost from the signal waveform due to the restricted bandwidth of the transmission waveform may effectively be restored to the signal applied to the cathode-ray tube, the picture signal applied to the cathode of the tube 5 is also applied with reduced amplitude and after integration by the network comprising potentiometer 6 and stray capacity 11 to the grid 8 of the tube 5. If desired, an actual capacitative component may be included in addition to the stray capacity. On account of the delay effectively introduced by the integrating circuit it may also be desirable to insert a delay network into the circuit to delay the signal applied to the cathode of the valve. In an alternative arrangement an integrating circuit is supplied from the cathode of a valve whose anode is coupled to the cathode of the cathode-ray tube. In a further arrangement, the second signal is derived by a circuit effecting double-differentiation. As a further alternative the two signals may be derived from separate receivers receiving the same radio transmission. In the arrangement shown in Fig. 7, the second signal is taken from the cathode circuit of the valve 42 whose anode load is such as to give the valve a voltage amplification factor of unity, thus compensating for the loss of gain at low frequencies.