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SERIAL · BASICS

What Is RS-232?

RS-232 is a long-established serial communication standard that connects two devices, sending data one bit at a time over separate transmit and receive lines. It is simple and widely supported, often through a 9-pin D-sub (DB9) connector, and is still common on industrial computers for instruments, scales, PLCs and legacy equipment.

01

The Short Answer

RS-232 measures each signal against a common ground, which makes it simple but sensitive to electrical noise and limited to short cables. It runs full duplex, sending and receiving at the same time, and includes optional handshaking lines that some older equipment still relies on.

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    Lab and test instruments Spectrometers, analysers and meters often report over RS-232.
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    PLCs and controllers Configuration and programming ports.
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    Scales and readers Weighing scales, barcode and card readers.
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    Legacy equipment Machines that outlive the computers controlling them.
02

Why It Matters

For longer or noisier runs, RS-422 and RS-485 take over; our RS-232 vs RS-485 FAQ compares them. The British Steel case study shows serial on M12 connectors linking panel PCs to plant equipment, and our M12 A-coded FAQ covers the connector.