Abstract: A velocity compensator arrangement for a synchronizer which includes an input oscillator, main store and output oscillator in which the controlling voltage of the input oscillator is sampled during one line and compared with the controlling voltage for the next line. Any voltage difference is converted into digital form and this is stored in a digital store until the corresponding line is read out from the main store. The phase of the output oscillator is shifted in dependence on the voltage difference held in the store. This store may comprise part of the main store or be an independent store.

Abstract: A video time base corrector includes an analogue-to-digital converter for converting an incoming analogue video signal to digital form, and a store for receiving successive lines of video information in digital form from the converter. A digital-to-analogue converter converts the digital output signal from the store into analogue form.Control means are provided for writing-in and reading out the digital information into and from the store. A triggered voltage controlled input oscillator determines the rate of conversion of the analogue signal to digital form and the rate of writing into the store. An output oscillator controls the rate of reading out of the digital information from the store and the rate of conversion into analogue form.Sampling means sample the input oscillator controlling voltage during one line and measuring means detect any voltage difference in the controlling voltage during successive lines.

Abstract: A sub carrier phase shifting circuit for use in digital television equipment comprising at least two monostable multivibrators connected in cascade. The sub carrier signal is applied to the first multivibrator. Adjusting means are connected to the control inputs of each multivibrator for adjusting the monostable period of the multivibrators. On receipt of an edge of a sub carrier wave the first multivibrator is driven from a first state to a second state whereby the first multivibrator effects a change of state at its output. The first multivibrator resets to its first state after the monostable period determined by the adjusting means to give an output delayed in relation to the edge of the sub carrier wave. The delayed output causes the second multivibrator to be driven from one state to its other whereby the second multivibrator effects a change of state at its output.

Abstract: A generator system for producing advanced mixed synchronizing pulses and comprising an equalizing pulse detector capable of detecting the presence of a first equalizing pulse of a mixed synchronizing pulse received at its input and a broad pulse generator. Delay means are provided for inhibiting the generation of the broad pulses for a preset period after the detection of the first equalizing pulse. The delay period is less than the period between the first equalizing pulse and the first broad pulse received whereby the broad pulses from the generator are producible in advance of the broad pulses received at the generator input. The generated pulses are added to the original mixed sync. pulse train whereby a mixed sync. pulse train is producible at the generator system output in which the original broad pulses and some of the equalizing pulses are replaced by the generated broad pulses.