G1 discrete and analog I/O

Although typically not recommended for new development, reliable G1 I/O modules are still used in Optomux, Pamux, and direct I/O systems.

The red-black-yellow-white color-coding scheme Opto 22 designed for G1 digital was later used for G4 and SNAP I/O, and it remains the standard today.


First developed in 1978, G1 is the first generation of digital I/O modules with plug-in racks for microprocessor-based control. G1 (also called "Standard I/O") quickly became the world standard form factor for I/O and created the component market for computer-based I/O.

Five years later we added G1 analog: the first optically isolated analog I/O modules with intelligent racks, marking the beginning of a new era in computer-based automation.


Need additional G1 I/O modules?

See discrete I/O used with racks PB4HPB8HPB16H, and PB16HC: See analog I/O used with racks PB4AHPB8AH, and PB16AH:

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