What Is a COM Port (RS-232 / RS-485)?

A COM port is the connection interface that lets computers exchange data with other devices through serial communication. In industrial automation it can be used to communicate with PLCs, barcode readers, measuring instruments, sensors and various control equipment.

RS-232 and RS-485 are different electrical standards used in serial communication.

• RS-232: Generally used for short-distance, point-to-point communication.
• RS-485: Over longer distances and in environments with electrical noise, with proper installation it can support connecting multiple devices to the same communication line.

When choosing an industrial PC, check which communication standard the devices use, how many ports are needed and whether the communication protocol is supported. The presence of a physical port does not necessarily mean the required protocol or software support is available.