Patent GB-1224917-A (GB)
Title: Method and apparatus for changing a simultaneous television signal to a line sequential signal and vice versa
IPC: H04N11/22
Filed: 1968-07-17
Abstract: 1,224,917. Television. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 17 July, 1968 [20 July, 1967], No. 34081/68. Heading H4F. An arrangement for converting an n-channel simultaneous colour signal to a sequential signal and vice versa is described and may be used for recording and replaying the simultaneous signal in sequential form on and from a tape recorder. Features are: synchronizing signals are only carried on some of the nchannels, overall synchronizing of the switching elements is obtained by using the picture or field synchronizing signal. In the simultaneous/sequential section shown in Fig. 2, the simultaneous colour signal is split into its R, G, B components which are fed on channels 1, 2, 3 respectively to switching element 4. Synchronizing pulses at 20 are added to the G and B signals by means of addition circuits 25 and 26. Switching element 4 is synchronized at a line-switching rate by the output of a 3-position ring counter 21 fed with the synchronizing pulses. In order that the picture synchronizing signal shall always be transmitted with the G signal, the picture synchronizing signal is separated out at 27 and fed to a control circuit 28 which, by means of monostables 30 and 31 and bi-stable 29, generates a pulse which brackets off occurrence of said synchronizing signal and which is fed to set the ring counter 21. The line sequential signal thus appears on line 5, the B and G signals being accompanied by synchronizing signals, the G signal also containing the picture synchronizing signal. In the sequential/simultaneous section shown in Fig. 3, the sequential signal of Fig. 2 enters at 7 and is passed to three switching elements 13, 14 and 15, directly (channel 8), via a oneline period # delay 11 (channel 9), and via two line period delays 11/12 (channel 10) respectively. The complete synchronizing pulse train is reconstituted by adding at 34 the outputs of sync. separators 32 and 33 from channels 8 and 9. The synchronizing pulse train is fed to a ring counter 36 which controls the position of the switching elements 13, 14 and 15, each of said elements lagging one channel behind the next. The picture sync. pulse is extracted by separator 38 and blocking circuit 37 provides a signal which synchronizes counter 36. The reformed simultaneous R, G and B components appear on lines 16, 17 and 18, each component comprising every third line in the original simultaneous signal repeated twice and with the intervening lines of the original discarded. Synchronizing pulses are removed by means 43 and 44. In the arrangement of Figs. 4 and 5 (not shown) the three components on lines 1, 2 and 3 are the chrominance and luminance signals (R-Y), (B-Y) and Y respectively. Synchronizing signals are fed to the Y channel only. The complete synchronizing pulse train must therefore be reconstituted by summing the outputs of all three channels 8, 9 and 10. In the arrangement of Figs. 6 and 7 (Fig. 6, not shown) the (R-Y) and (B-Y) components are combined into one channel by having the (R-Y) component amplitude modulate a carrier and having the sideband thus formed added to the (B-Y) component. Switching element 4 now becomes a two-way switch and ring counter 21 a bi-stable. Switching element 58 extracts the Y component and synchronizing signal and switching element 59 extracts the compound of the (B-Y) and (R-Y) components. Separation of these components by low-pass filter 60, high-pass filter 61 and demodulator 62 then occurs.