| 摘要 |
PURPOSE:To prevent generation of mis-transmission by providing a circuit suppressing noises generated from a line driver when a power supply of a communication line driver is turned on to bring the level of a transmission line at a transient voltage at power application/interruption to a low level. CONSTITUTION:When a power supply 6 applies a voltage to the communication line driver 4 and a level of a signal -PON of a power supply on/off control line 1 is logical 0, the power supply 6 is turned on and when the -PON is logical 1, the power supply 6 is turned off. The power supply 6 and the driver 4 are provided with noise elimination TRs 7, 8 and the TR8 is controlled by a signal -INH of a noise elimination control line 2. When the communication is started, the level of the signal -INH is brought to logical 0, the TRs 8, 7 are turned on and then the signal -PON is brought to logical 0, the power supply 6 is turned on. Bipolar voltages at outputs +V, -V are made equal according to the application of the power supply 6 and the power supply is made stable, then the level of the signal INH is brought to logical 1, the TR7 is turned off so as to allow a communication line driver input 9 to drive a communication line output 3. |
