An apparatus and method for determining the tuned frequency of a digital repeater (2) solely through the use of external connections. A pulse burst (30) at a preselected transmission frequency, produced by generator circuitry (4), is inserted into repeater (2) to cause the timing circuit of the same to oscillate for a predetermined time interval (25). After burst (30) and during interval (25), a plurality of sequential sampling pulses (26, 27) is fed to repeater (2) and regenerated by same. This format of burst (30) followed by sampling pulses (26, 27) is preferably repeated a number of times. Counter (10) measures the average time interval between the regenerated sampling pulses and determines the tuned frequency.