For instance, a radio wave at 1 MHz has a period of 1 µs, and the EH phase difference changes about 45 degrees between to . Thus, a 1 degree EH phase difference in a 1 MHz signal corresponds to a range difference of about and 1/360 of the period or 27.78 ns difference in time between the electric and magnetic signals. Down-converted to a 1 kHz audio signal, the period becomes 1 ms, and the time difference required to measure becomes 27.78 µs. A comparable time-of-flight (TOF) or Time difference of arrival (TDOA) system would require 2 ns to 4 ns to make the same measurement.