As shown on the figure 11-6, the fishing circuit consists of timing circuit and audio circuit. 555, RP1 and C1 make up the single shot circuit. The definite time: td=1.1RP1C1. The maximal definite time given by the figure is 15s.IC2 adopts the muisc integrated block HY101. In the IC1`s definite time, J is pull-in, the contact J1-1 and J1-2 is closed, H1 and..