GB1315312A - Cathode ray tube display devices - Google Patents

Abstract

1315312 Television BRITISH BROADCASTING CORP 29 June 1970 [31 March 1969] 16791/69 Heading H4F Relates to monitoring apparatus then enables television engineers to superimpose upon a television picture a display indicating the magnitude, waveform or timing of an electrical signal associated in some way with the television signals producing the picture or derived from, for example, television recording or reproducing apparatus associated with the monitor, i.e. it is possible to check whether the several recording heads in a video-tape recorder are all functioning satisfactorily. It is also possible to monitor the chrominance level as derived from the colour bursts, or the timing of synchronizing pulses. In a known arrangement, Fig. 1, the video signal from a monitoring reproducing head of a video recorder 11 is fed via a low pass filter 13 to a comparator 14 where it is compared with the output of a line frequency sawtooth generator 15, and the resulting pulse signal differentiated 16 and superimposed on the television monitor 12 picture display. If the level of the signal from filter 13 changes, spots 21 and 22 are produced on the display screen Fig. 3. According to the present invention a display as shown in Fig. 6 is produced by passing the output of the comparator via a one line period delay 25, Fig. 4, an inverting amplifier 23, an incremental delay 24 (few microseconds) and half amplitude attenuators 26 and 27 to a summing device 28, the output of which is rectified 29. With a field frequency sawtooth generator a waveform recurring at line frequency and containing high frequencies may be displayed (Figs. 7 and 8, not shown) whereas with a line frequency sawtooth generator only low frequency signals may be displayed. Without line delay 25 a differentiated output similar to the known arrangement of Figs. 1 and 3 would be produced.