在要求通信距离为几十米至上千米时,广泛采用RS-485收发器。RS-485收发器采用平衡发送和差分接收。即在发送端,驱动器将TTL电平信号转换成差分信号输出;在接收端,接收器差分接收,将差分信号变成TTL电平。因此,它具有抑制共模干扰的能力,加上接收器具有高的灵敏度,能检测低达200mV的电压,使传输信号能在千米以外得到恢复。 RS-485 transceiver is widely used when the communication distance is required to be several tens of meters to the top of thousands. RS-485 transceivers use balanced transmit and differential receive. That is, at the sending end, the driver converts the TTL level signal into a differential signal output; at the receiving end, the receiver receives the difference and changes the differential signal to the TTL level. Therefore, it has the ability to suppress common-mode interference, coupled with the receiver with high sensitivity, can detect the voltage as low as 200mV, so that the transmission signal can be restored beyond kilometers.