Abstract: A filter for filtering analog or digital samples using two sections, each including a multiplier stage having a plurality of multiplier sections, each with a respective output but a common input for applying a plurality of coefficients to a sample input to the multiplier stage, and a delay and summing network comprising a plurality of delay sections and alternate summing networks connected in series, the output of one of the multiplier sections being connected to the first delay sections in the series with each output of the other multiplier sections being connected to a respective summing network, the delay and summing network of one section being interleaved in series with the delay and summing network of the other section, and further comprising means for omitting alternate samples.

Abstract: Vertical synchronization information in a multiplexed analogue component (MAC) television signal is included in a line scan period, the amplitudes of the waveform being chosen so as to represent a position in the color space outside that occupied by the picture signal; preferably, the amplitudes are chosen to be at the limits of the picture signal amplitude. By these means, the normal horizontal synchronization information can still be included in the form of transitions 1 and 2, and the chance of the synchronization and picture signals interfering with each other is minimized.

Abstract: A device for providing a selectively variable proportion of an electrical signal, which can be used instead of a conventional resistive track potentiometer, is disclosed. The device comprises two switching devices, typically CMOS transmission gates, connected in series between two inputs for receiving the electrical signal, an output at the series connection of the switching devices, and a control circuit for cyclically switching the switching devices between high and low conductivity states. The control circuit is so arranged that when one of the switching devices is in its high conductivity state, the other is in its low state and vice versa, and the control circuit is arranged to control selectively the relative durations that the devices remain in their different conductivity states.