| 摘要 |
PURPOSE:To omit a circuit or software for the formation and control of a transmission-enable signal by outputting transmission data from a terminal equipment to a central controller through a three-state differential output circuit and using the inverted signal of the transmission data as a transmission enabling signal of the three-state differential output circuit. CONSTITUTION:Under no polling from the central controller 20, a terminal to which transmission data SD are applied is in the high level, the output of an inverter 214 (or 224) is turned to the low level and the output is applied to control terminals of output circuits 212, 213 (or 222, 223), so that the outputs of the output circuits become transmission-disabled status. If bowling to a terminal equipment 21 (or 22) is applied, the transmission data SD is changed, and during the period of low level of the data SD, the output of the inverters 214, 224 are turned to the high level and the output circuits 212, 213 (or 222, 223) are turned to the enabled status. |
