说明：  阐述了RS-485总线规范，描述了影响RS-485总线通信速率和通信可靠性的三个因素，同时提出 了相应的解决方法并讨论了总线负载能力和传输距离之间的具体关系。
(Described the RS-485 bus specification, describes the impact of RS-485 bus communication speed and communication reliability of the three factors, while the corresponding solutions presented and discussed the bus load capacity and the specific relationship between the transmission distance.)