Abstract: A variable pulse rate circuit for correlating a locally generated code with code that is being transmitted by a space vehicle. A computer means is used for providing a binary word to a latch. The binary word in the latch is used in turn by a delay line, to control the amount of delay that is presented to pulses. The pulses are emitted by a pulse generator having a fixed rate reference. The pulse rate, of pulses being emitted by of the delay line, is varied from the reference pulse rate. This variation is the result of computer means that rapidly changes the amount of delay of the delay line. The pulse rate and the pulse phase are varied in order to cause a locally generated code to become phase aligned with the code received from the space vehicle. The space vehicle is tracked using the variable pulse rate circuit.