Abstract: In an electro-mechanical distribution system having plural units each comprising a valve/switch and dual sensors, a computer is associated with each unit so as to process sensor information and control the valve/switch. According to the control logic, a unit is either in normal mode or fault mode. The fault mode begins with a transient waiting period and may continue on to a series of steps. A step waiting period (wherein the valve is closed) may be followed by the step testing period (wherein the valve is closed) of the same step; a step testing period may be followed by the step waiting period of the next step. Fault mode is triggered if at any time during normal mode either sensor detects a fault condition. Normal mode is triggered if at any time during fault mode both sensors concurrently detect a normal condition.