RS-232、RS-422与RS-485都是串行数据接口标准，最初都是由电子工业协会（EIA）制

订并发布的，RS-232在1962年发布，命名为EIA-232-E，作为工业标准，以保证不同厂家产品

之间的兼容。RS-422由RS-232发展而来，它是为弥补RS-232之不足而提出的。为改进RS-232

通信距离短、速率低的缺点，RS-422定义了一种平衡通信接口，将传输速率提高到10Mb/s，

传输距离延长到4000英尺（速率低于100kb/s时），并允许在一条平衡总线上连接最多10个接

收器-RS-232, RS-422 and RS-485 serial data interface standards are the first by the Electronics Industry Association (EIA) and published in, RS-232 issued in 1962, named for the EIA-232-E, as the industry standard to ensure that different manufacturers of compatible products. RS-422 by the development of RS-232, which is designed to remedy the lack of RS-232 made. RS-232 to improve the short-distance communications, the shortcomings of low-rate, RS-422 defines a balance between communication interface transfer rate up to 10Mb/s, transmission distance was extended to 4000 feet (at rates of less than 100kb/s), the and allow the balance on a bus to connect up to 10 receivers