Constructing a WIO System begins with a WIO Radio Kit. The kit includes a factory-paired Radio set and all the mounting hardware necessary for installation onto 35 mm DIN rails. Then, simply add matching pairs of I/O Modules to get just the right mix of I/O. There are three available I/O Modules to choose from: Analog 4-20 mA, Analog 0-10 Vdc, and Digital. Each paired Radio System provides a secure I/O link using AES encryption. You can safely and reliably run multiple radio pairs in close proximity.