Simpson's series of elapsed time meters features a six-digit readout with no reset capability, making them virtually tamper proof. Each true-time elapsed time meter is ruggedly constructed and records the "on" time of electrical equipment. They are widely used in factory environments where there is a need to accumulate running time and monitor life and performance records on AC and DC powered equipment. All hour meters are connected in parallel with the equipment being monitored. The synchronous motor provides accurate hour indication. Model 109ET has a 10-80 V DC input as a standard feature. An optional plug-in AC converter module can also be ordered with the model 109 ET. Choose from Century, Wide-Vue, Rectangular or Round case styling to match other instruments.