There is no universally accepted external control system; the control must fit the situation. So the focus here will be on the importance of integrating various controls through the systems approach. Preliminary control is designed to anticipate and prevent possible problems. To be successful, we need to anticipate and prevent problems rather than solving problems after they occur.

Concurrent control is action taken to ensure that standards are met as inputs are transformed into outputs. It is more economical to reject faulty input parts than to wait and find out that the finished output does not work properly. Rework control is action taken to fix an output. Rework is necessary when preliminary and concurrent controls have failed. Most organizations inspect the final output before it is sold.

Damage control is action taken to minimize negative impacts on customers/stakeholders due to faulty outputs. When a faulty output gets to the customer, damage control is needed. The only way to continually increase customer satisfaction is to use feedback from the customer and other stakeholders to continually improve the products and services.