Apparatus for adjusting the output frequency of a frequency divider comprising a circuit constituted of a resistance R and a capacitor C for receiving output pulses from the divider. A comparator is connected to the RC circuit and to the divider for receiving normal pulses from the divider and pulses with a delay t proportional to the time constant RC for comparing the delay pulses with the normal pulses to produce control pulses of duration t. A switching arrangement is coupled to the comparator and to the divider for switching the rate of the divider from an initial rate n.sub.o to a value n' during the duration of the control pulses. The divider has a plurality of outputs and when n' is greater than n.sub.o the RC circuit is connected to one of the outputs while when n' is smaller than n.sub.o the RC circuit is connected to another of the outputs.