KEP Low Cost Hour Meter H57. These meters are mainly used for monitoring the running time of machines, apparatus and instruments as well as for recording maintenance time, warranty time or rental use time. A synchronous motor operating through a gear train drives the number wheels for the display of full hours 1/10 h and 1/100 h. On AC-versions, the main supply (50 or 60 Hz) is used as frequency standard. On DC-versions the exact frequency generated by means of a quartz crystal. A rugged and completely insulated plastic housing provides substantial protection against environmental influences.