dumped from the system resulting in needless waste as well as flooding of the area where the fire truck is located more recently electronically operated pressure control systems have been introduced three such systems are disclosed in u s pat nos 3 786 869 4 189 005 and 7 040 868 herein referred to as the u201c 39 869 patent u201d u201c 39 005 patent u201d and u201c 39 868 patent u201d to mcloughlin the subject matter of which is incorporated herein by reference in the 39 869 and 39 005 patents the desired output pressure is dialed in or otherwise transmitted to a control box on board the fire truck where it is compared to the actual output pressure as measured by a transducer any difference between the desired and actual output pressures is converted to an electrical signal which is fed to a dc motor which increases or decreases the rpm of the centrifugal pump as needed until the desired output pressure is reached these prior systems may require a long response time in a servo mechanism controlled engine too much time can pass before the appropriate rpm and correct discharge pressure are reached this is especially troublesome during transient events such as overpressure spikes where the system 39 s response time is greater than the length of the event furthermore no allowance is made for situations such as when the engine is already at idle and the incoming pressure suddenly increases or is higher than desired such as can happen when the pump is connected to a hydrant the 39 868.