What type of control system does not compare the output with input for regulation?

An open-loop system is characterized by its lack of feedback to compare the actual output against the desired output. In this type of system, the input is processed to generate an output without any adjustments made based on the output's performance. This means that once the instruction is given, the system executes without any consideration for the result it produces; it operates under the assumption that the process will work correctly without needing to monitor or adjust based on the output.

For example, consider a simple toaster. You set it for a certain time, and it toasts the bread for that duration without adjusting based on how toasted the bread actually is. If the bread is burnt or insufficiently toasted, the toaster has no mechanism to rectify its performance because it doesn’t check the output against any criteria.

In contrast, closed-loop systems utilize feedback to compare the output with the input, enabling them to correct any discrepancies, while feedback systems inherently depend on this monitoring to function effectively. Automated systems often utilize elements from both open and closed-loop controls but are not exclusively defined by one type. Thus, the lack of feedback in an open-loop system makes it distinct from the others listed.