Abstract: A circuit is arranged to derive the internal vertical synchronizing signals and field identification signals for a digital television signal. The circuit operates from the internal horizontal synchronizing signals and the separated external synchronizing signals and employs a sign inverter, an accumulator, an absolute value device, a comparator, a counter and AND gates, as well as an OR gate. These components, as coupled, produce the above-noted signals by digital generation and requires no subcircuits that are independent of the horizontal oscillator which horizontal oscillator is arranged in a phase lock loop.

Abstract: This circuit simultaneously provides the sine- and cosine-function values for one and the same digital argument from any of the quadrants of the sine and cosine functions. Stored in the two halves of a read-only memory are the unsigned function values of the first half-quadrant of the cosine function in the direction of increasing arguments and of the second half-quadrant in the direction of decreasing arguments, respectively. The number of bits of the argument is greater than the number of bits of the function values, including the sign bit, by two. By skillful inversion of the addresses and the read-out function values using multiple-inverter blocks in conjunction with multiple-switch units sine- and cosine-function values can be generated for all four quadrants both in the one's and in the two's complement code. If the argument is formed by an accumulator fed with the frequency determining digital word, the digital circuit is a digital sine-/cosine-wave oscillator.