GB994120A - Apparatus for the regeneration of television signals - Google Patents

Abstract

994,120. Television. FERNSEH G.m.b.H. Sept. 27, 1963 [Sept. 28, 1962], No. 38143/63. Heading H4F. Apparatus for the regeneration of television signals containing a test line occurring within the standard vertical blanking interval comprises means controlled by horizontal and vertical blanking signals derived from the synchronizing signal contained in the television signal for producing in the regenerated signal a constant interference-free blanking signal, upon which is added a new synchronizing signal, likewise derived from the television signal, in which the derived vertical blanking signal is interrupted at least for the duration of the test line. The relationship between the white impulse in the test line and peak white in the picture signal is thus maintained since the test line is not blanked out. In the embodiment described the test line (Fig. 2b, not shown) is transmitted at the end of the vertical blanking interval (Fig. 2a, not shown) and the duration of the derived vertical blanking impulse (Fig. 2c, not shown) is made so that it terminates before the commencement of the test line. The television signal to be regenerated is received at 1 and fed to a device 2 in which alternating voltages superimposed upon the signal, such as hum voltages, are suppressed, control 20 of a clamp circuit serving for adjustment of the peak white level, and then to a device 3 in which it is blanked, control 30 serving for adjustment of the black level, and then to a device 4 in which the peak white level of the signal is limited at a potential determined by the setting of control 40 and finally to a device 5 in which a new synchronizing signal is added so that at the output 6 the complete regenerated television signal appears. The signal received at 1 is also applied to an amplitude filter 7 from which the horizontal and vertical frequency impulses are made separately available and in device 8 the required blanking signal components are developed and applied to device 3, and in device 9 new re-shaped synchronizing signals are formed and applied to device 5, their amplitudes being adjusted by control 90. So that the test line signal may be blanked out when it is severely distorted a switch 10 is provided, by means of which the whole of the vertical blanking interval including the test line may be blanked out and regenerated. The test line which comprises a peak-white impulse followed by a grey step-wedge may be used for monitoring purposes or for stabilizing the signal level.