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SERIAL · COMPARISON

RS-232 vs RS-485: What Is the Difference?

RS-232 is a single-ended serial link between two devices over a short cable, typically up to about 15 m. RS-485 uses a differential signal over a twisted pair, so it resists electrical noise, runs up to about 1,200 m and lets many devices share one bus. RS-422 sits between them: differential, long distance, one sender to several receivers.

01

The Short Answer

Many industrial computers have serial ports that can be switched between RS-232, RS-422 and RS-485 in the BIOS or with jumpers, so one machine can talk to an old instrument on RS-232 and a bus of controllers on RS-485. The wiring and the far-end device decide which mode to use.

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    RS-232 Short, point-to-point links to instruments, scales, readers and legacy equipment.
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    RS-422 Long, noisy runs from one controller to one or a few receivers.
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    RS-485 Multi-drop buses such as Modbus RTU and PTZ camera control.
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    Selectable ports Choose a computer with protocol-selectable serial if the site mixes all three.
02

Why It Matters

Our RS-232 FAQ, RS-422 FAQ and RS-485 FAQ cover each standard. The British Steel case study shows protocol-selectable serial on rugged panel PCs, and our rugged panel PCs cover the range.