Abstract: The present invention provides a feedback control system using at least one operating personnel for controlling a system or a function in a system. The control results from sequential manual interruption by the operator of the fluid flow at the discharge end of a flowing system within a preset time period. As the liquid flow is interrupted, changes in flow characteristics, such as those affecting flow or pressure, for example, are instantly caused within the system. A transducer connected to the system senses these changes in flow characteristic and subsequently transduces them into electrical impulse signals that correspond directly to the sequential interruptions occurring at the discharge end of the system. An electronic circuit counts these electrical impulses, and causes relay switches to change state, causing electromechanical functions in the system to occur.