| 摘要 |
PURPOSE:To generate an output from the signal processing circuit when expected conditions have completed to prevent malfunctions, by providing a detector to detect characters peculiar to the metallic body to be detected, a level detector operated according to the magnitude of the detection signal, and so on. CONSTITUTION:When metallic body 1 of the object to be detected, for example, a train approaches magnetic detector 2 in a constant speed, low-level detector 3 reacts at point A1 of low level LL to send the detection signal to signal processing circuit 9 through the magnetic detector generates the voltage shown in the figure. When the train approaches furthermore, the magnetic detection signal voltage is increased, and middle level detector 4 is operated at point B1 of middle level ML. This operation signal is sent to signal processing circuit 9 also. When the train passes through the magnetic detector to reduce the magnetic detection signal voltage and detector 4 detects point B2 of ML again, signal processing circuit 9 sends the output signal to output driving circuit 10 under three conditions of (a) no operation signal exists in high-level detector 5, (b) point B2 is detected with detector 4, and (c) counter number of counter 7 is ''1''. |
