| 摘要 |
PURPOSE:To improve the reliability of data by detecting a reception level at a terminal device of a bus transmission line and changing a signal transmission level of a driver and a threshold value of signal identification for a receiver in response to the result of detection to prevent error generation at reception by the terminal device and a master device. CONSTITUTION:The master device and the terminal device are connected respectively to a receiver 1 and a driver 2 of the transmission level control system and the reception level from the master device is detected by a reception level detecting circuit 3. The voltage across variable resistors RV1, RV2 of the receiver 1 is changed depending on the reception level detected by the circuit 3 to change the threshold level of amplifiers A1, A2 amplifying the reception input. Further, the voltage across variable resistors RV3, RV4 of the driver 2 is changed in response to the reception level detected by the circuit 3, the voltage controls the operation of transistors TRs 1-8 to change the output level from the transformer T0. Then error generation at the reception of the master device and terminal device is prevented to improve the reliability of data.
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