The ABB DI801 (3BSE020508R1) is a digital input module. It is part of ABB's System 800xA series, which is a comprehensive distributed control system used in various industrial applications. 

The DI801 module is designed to interface with digital input signals from field devices or other equipment and transmit them to the control system for processing. It offers multiple channels for connecting digital signals, and it supports various input signal types, such as discrete on/off signals.

The specific features and specifications of the ABB DI801 digital input module may include the number of input channels, input voltage or current levels supported, isolation capabilities, and diagnostic functionalities. 

ABB DI801 3BSE020508R1 Digital Input Module Datasheet