The Cable Height Meter emits short bursts of sound which originate from the cone-shaped transmitter. The microprocessor in the instrument calculates the elapsed time for the bursts of sound to be reflected from the cable back to the instrument. The result can be displayed in either feet and inches (imperial)or meters (metric) format. To account for the fact that speed of sound varies with temperature, a temperature sensor mounted at the front of the instrument senses the actual air temperature.