| 摘要 |
PURPOSE:To obtain a compact and light-weight frequency selecting circuit which has the excellent frequency characteristics with quick response and high fail-safe performance, by providing a shift register, two gate circuits which detect the levels of all bits of the recording information and an FF. CONSTITUTION:An external synchronous type shift register 1 stores successively high and low levels H and L of an input rectangular wave FP of 1:1 duty to be detected in accordance with a clock pulse CP. The register 1 has a capacity of the number of bits corresponding to the pulse time duration equal to half cycle of the highest frequency of the wave FP. A gate circuit 2 detects that all bits of the information stored in the register 1 are set at H levels; while a gate circuit 3 detects that all bits of said information are set at L levels respectively. An R-SFF4 is driven by the outputs of the circuits 2 and 3, and a rectangular wave signal having the same frequency as an input wave is delivered. Thus it is possible to obtain a compact and light-weight frequency selecting circuit which has the excellent frequency characteristics with quick response and high fail- safe performance. |
