Actually what I meant to convey was this:

Assume you have a square pulse to measure. In the reciprocal method you count the number of pulses ( generated by the gating circuit -say at 1 micro sec intervals )between the first rising edge of the signal and the NEXT rising edge or in other words the gate is controlled by the input signal. If ( a big if ) the above said NEXT rising edge is missed then the gate does not close. That is what I meant.

Not sure if I made it clear...

Raghu