Abstract: In a method of transmitting and receiving Multiplexed Analog Component (MAC) television signals by producing first chrominance component and luminance component signals representing lines of a television signal capable of reconstruction in a conventional MAC television receiver to produce a first television picture having a first aspect ratio and a first number of lines and wherein the component signals for each line are time-compressed and placed sequentially at times appropriate to allow reconstruction of the television picture but occupying less than the whole line time, the improvement whereby further luminance component and chrominance component signals are generated and added to portions of the television signal not containing the first signals such that the further component signals are capable of being reproduced together with the first signals to produce an extended definition picture with the further component signals not interfering with the picture reproduction from the first chrominance and lumin

Abstract: A multiplexed analogue component (MAC) television signal is encrypted for transmission and reception by authorized recipients only by dividing the signal into blocks and reordering the blocks prior to transmission. The signal within each block remains in its original order. Preferably, the signal representing one line of video is split into blocks which are reordered within the line time to cause translation or rotation of analogue components. Alternatively a group of lines may be processed as a group to cause reordering of the analogue components between lines. The preferred arrangement does not split the blocks of analogue signals already present in the MAC signal. The receiver is arranged to receive information regarding the encryption technique with the television signal and to reorder the blocks constituting the received signal whereby to reconstruct the original signal.