These systems use signals transmitted from several transmitters around the globe. Since the radio signals travel at the same speed of 186000 miles / sec, the signals from the different ground transmitters will not be received on the aircraft at the same time.
A calculation based on the reception time difference between these signals from different ground stations results in a navigational position fix.
The aircrew use a Cathode Ray Tube (CRT) to read these radio signals. [James P.169] [US Navy Air Nav manual P.345]