Publisher Summary This chapter explores some practical control systems such as digital engine control systems. It describes representative control systems that are not necessarily based on the system of any given manufacturer, thereby giving the reader an understanding of the configuration and operating principles of a generic representative system. The systems described in the chapter are a compilation of the features used by several manufacturers. The microcontroller under program control is possible for generating the electrical signals that operate the fuel injectors and trigger the ignition pulses. This chapter also discusses secondary functions of the digital engine control systems. The digital engine control system has been made possible by a rapid evolution of technology, and innovations such as integrated engine control system, oxygen sensor improvements, fuel injection timing, automatic transmission control, torque converter lock-up control, traction control, and hybrid vehicle powertrain control. The chapter concludes with a discussion of hybrid vehicle control systems in which propulsive power comes from an IC engine or an electric engine, or a combination of both.