| 摘要 |
PURPOSE:To detect the production of failures in an input circuit automatically, by giving a test pulse periodically produced to an input circuit having a plurality of isolation circuits and monitoring the output of an isolation circuit on a display device. CONSTITUTION:An input signal (d) given between terminals IN1-INn and a common terminal G is inputted to a latch circuit LT via photo couplers PC1-PCn and inverters IV1-IVn to illuminate light emitting diodes LD1-LDn. The circuit LT holds the input signal according to a stroke pulse SP (c) from a pulse generator PG and outputs a pulse (e). A test pulse TP (a) is generated and applied to the PC1- PCn at a different time from the SP (c) from the PG, and the output passes through the IV1-IVn and a gate G11 and an L level signal is inputted to an AND gate G12. The PG generates a sampling pulse (b) at almost the center of the TP (a) and it is applied to the gate G12, and if either of the PC1-PCn is in failure, the gate G12 outputs an H level signal to illuminate a light emitting diode LD21 for the display of failures. |
