An input rectangular signal is differentiated and short impulses are formed from its edges. These impulses write the content of counter A to a latch that clears the counter after a very short time. Counter A counts impulses of the frequency fo that are much greater than that of the input signal. The pulses come from an impulse generator. Thus, the number, which is written to the latch, expresses the number of these impulses between the edges of the input signal. The impulses from the same generator pass to (reverse) counter B. The carry impulse loads the content of the latch to counter B. The latch is connected with the reverse counter such that the number written to this counter is 2M times smaller than the number introduced to the latch.
This can be readily achieved by omitting most significant bites -f counter B. Because the number loaded to counter is 2M times smaller than the number in the latch, the carry impulses of counter have frequency 2 times greater than the frequency of the impulses at the output of the differentiator. The carry impulses are fed to a D flip-flop, which divides their frequency by two. In this way, the output frequency is 2 greater than input frequency fL as long as the frequency of impulse generator/ is much greater than 2Mf.