Frequency synthesizer

A frequency synthesizer of the type which selects pulses from a clock pulse source, of higher pulse frequency Fc than the required output frequency Fo, in order to provide said frequency Fo;

• the synthesizer including an adjustable accumulator which, for each input clock pulse thereto, adds a preselected adjustable increment Y to the accumulated value in the accumulator and gives an output pulse each time an accumulated value C, in which C is equal to or greater than Y, is reached or exceeded, any excess being left as a residue Rn in the accumulator, characterized in that the synthesizer further comprises adjustable delay means coupled to said adjustable accumulator output for delaying each output pulse n from the accumulator, said delay means having a control input coupled to said accumulator for accessing the residue Rn therein, whereby the amount each output pulse n from the accumulator is delayed is a function of the residue Rn in the accumulator immediately after that output pulse.