G1 I/O Family Opto 22 G1 I/O Family features digital and analog I/O modules that use a red-black-yellow-white color-coding scheme. The G1 product lineup includes not only I/O modules but also sensors, controllers, switches, and cables. The digital I/O modules with plug-in racks are ideal for microprocessor-based control. The optically isolated analog I/O modules with intelligent racks are designed for computer-based automation. The Opto 22 G1 products are guaranteed for life.