PHASE DIFFERENCE MONITORING CIRCUIT

PROBLEM TO BE SOLVED: To provide a phase difference monitoring circuit, capable of reducing a circuit scale on condition that the phase difference of a present device frame pulse and a reception frame pulse is not so large. SOLUTION: This phase difference monitoring circuit for receiving a first frame pulse and a second frame pulse, counting the phase difference by the number of clocks and outputting it is provided with a phase difference counter 12 for performing counting only for a phase difference monitoring range and a decoder 13 for decoding the output of the phase difference counter 12 and outputting signals regarding polarity. The output of the phase difference counter 12 is outputted as phase difference signals, and the output of the decoder 13 is outputted as polarity signals.