GB1483488A - Circuit arrangements and methods for colour television signal receiving - Google Patents

Abstract

1483488 Colour television SONY CORP 19 Nov 1974 [29 Nov 1973] 50120/74 Heading H4F Colour television apparatus is controlled to automatically receive either a PAL colour television signal or a SECAM (Registered Trade Mark) colour television signal by a discriminator circuit 9 controlling a switch 8 to connect the output of either a PAL demodulator 7P or a SECAM demodulator 7S to a matrix 10. In the SECAM signal the B-Y subcarrier is at 4À25 MHz and the R-Y subcarrier is at 4À40625 MHz. The discriminator circuit 19 includes a band-pass filter (14, Fig. 6, not shown) to select the bursts of one of these SECAM subcarrier frequencies, occurring during every second line period, which bursts are passed via an envelope detector (16) to a half-line frequency tuned circuit (17) which provides an output when a SECAM signal is being received, this signal being converted into a D.C. signal which controls switch 8. If the band-pass filter is such as to select the bursts of 4À25 MHz it produces no output when receiving a PAL signal having bursts at 4À43 MHz, whereas if the band-pass filter is tuned to 4À42 MHz so as to select the bursts of 4À40625 MHz it passes all the PAL bursts at 4À43 MHz; in either case the half-line frequency tuned circuit provides no output when a PAL signal is being received and switch 8 connects the output of PAL demodulator 7P to matrix 10.