| 摘要 |
PURPOSE:To achieve the transmission of earth on an SR line even at a failure of a power supply device, by connecting a resistance division circuit for bias supply of a transistor switch to a logical sum circuit inputting an input negative power supply of the power supply device and an input negative power supply o another system. CONSTITUTION:A logical level SR signal 2 outputted from a logical circuit 1 is voltage-converted at a resistance division circuit 5 to control on/off of a PNP transistor (TR) switch 6, allowing to open or ground an SR signal transmission terminal 7. The logical sum between an input negative power supply from a power supply negative voltage input terminal 8 and that from a negative power supply input terminal 9 of a separate system, is taken at a logical sum circuit 10, and the output is applied to one end of the circuit 5 as a negative power supply. If the secondary output voltage of a power supply 3 is opened due to any cause, as far as either one of the negative power supply 8 or 9 is normal, the switch 6 turns on and ground is given to an SR signal transmission terminal 7. |
