What does the ground station for DME transmit to the aircraft?

The ground station for Distance Measuring Equipment (DME) transmits paired pulses to the aircraft. This method of transmission is essential for determining the distance between the aircraft and the ground station. The DME system works by sending out a pulse from the aircraft to the ground station, which then responds with its own pulse. The timing between these two sets of pulses allows the onboard DME equipment to calculate the distance based on the speed of light.

This paired pulse transmission is crucial for accurate distance measurement, as each pulse is specifically timed and spaced to provide precise information. The other options do not represent the function of DME: audio signals are not used in DME, continuous tones do not provide the necessary timing data for distance calculation, and visual messages are not transmitted in the DME system. Thus, paired pulses are the correct medium for transmission in this context.