Over the last several years, the use of D.C. solenoids and electronics to ensure safe and reliable diesel engine shutdown has grown significantly. These devices are used during normal engine operation and in the event of a malfunction. Applications include both on and off-highway vehicles as well as generator sets. The use of key start in off-highway equipment has also had a major impact on the use of D.C. solenoids. Reliability has been improved through the use of computerized coil design, constant volume protection boots, external switching and electronic timers. Testing methods (for vibration. shock and temperature extremes) have been developed to promote trouble free product life.