AAn HIL simulation must include electrical emulation of sensors and actuators. These electrical emulations act as the interface between the plant simulation and the embedded system under test. The value of each electrically emulated sensor is controlled by the plant simulation and is read by the embedded system under test (feedback). Likewise, the embedded system under test implements its control [[algorithms]] by outputting actuator control signals. Changes in the control signals result in changes to variable values in the plant simulation.
For example, a HIL simulation platform for the development of [[Anti-lock brake|automotive anti-lock braking systems]] may have mathematical representations for each of the following subsystems in the plant simulation:<ref name=brake>T. Hwang, J. Rohl, K. Park, J. Hwang, K. H. Lee, K. Lee, S.-J. Lee, and Y.-J. Kim, "Development of HIL Systems for active Brake Control
