We have now reached an important milestone in the book, and with this chapter we are moving from the theoretical foundations of ADRC to its applications. Putting ADRC in practice will almost always be in the form of a software-based implementation, be it in embedded systems or on PLC. Given the inherent discrete-time nature of the underlying target processor systems, it is obvious that the continuous-time variants of ADRC discussed so far are not yet the answer when asking for an actual implementation. To cross the line between “theory” and “practice” that has been established in the subtitle of this book, we will therefore present several discrete-time variants of linear ADRC with different feature sets in this chapter. All of them are ready for use in industrial practice and range from state-space to transfer function forms optimized for a low computational footprint.