This combination meter comprises a running time totalizer and an adding counter with a separate 7 digit display for each. In the standard version, the two meters are connected in parallel; the totalizer counts the number of pulses while the time meter totalizes the connect time. The time meter displays to hundredths of an hour (36 second intervals). A red visual indicator shows that the unit is operating. The unit is supplied with a clamp clip attachment for mounting and 2.16″ x 2.16″ (55mm) and 2.16″ x 2.16″ (72 x 72 mm) bezels are available as accessories. On AC models, the main supply (50 or 60 Hz) is used as the frequency standard. On DC models, the frequency is quartz crystal controlled. The HC77 is suitable as a replacement for the discontinued HC67.