| 摘要 |
PURPOSE:To attain to enhance the operability, the mass-productivity and the safety of a digital multi-meter main body, by prohibiting a function, a point and unit display without employing an external circuit when an option function is applied. CONSTITUTION:The display prohibiting circuit part 1 operated when an option function is connected in an one chip A/D converter LSI is constituted from a point mark decoder 2, NAND gates 3-5, a liquid crystal display drive circuit 6, inverters 7, 8 and pull-up resistance while a switch 10 and a liquid crystal panel 11 are externally connected to said circuit part 1. When the switch 10 is turned ON, the input of the inverter 8 and the output of the inverter 7 are fixed to an L-level. Therefore, the output terminals of the gates 3-5 are fixed to an L- level. As a result, the input of the drive circuit 6 is prohibited and the function, the point and the unit display of the panel 11 are prohibited. |
