The Eagle Signal HK series are electro-mechanical time totalizers. A synchronous motor drives a set of digit readout wheels to indicate the total time the unit is energized. The HK4 have six digit-wheels, including a 1/10 digit on hours and minutes, provide a fine, wide range of time measurement. The HK5 have five digit-wheels and features a front mounted reset wheel. It can be reset to zero at any time during its operation.