After the aircraft transmits its interrogation pulses, it then listens out for the response to its own "jiggered" pulses.

If the aircraft listened out on the same frequency, there is every chance that it could mistake reflections from the ground as the response from the DMEDME —Distance Measuring Equipment beacon — and thus display the distance to the ground and not to the DMEDME —Distance Measuring Equipment.

In older DMEDME —Distance Measuring Equipment systems, this lockon is detected by an echo protection circuit (EPCEPC —Echo Protection Circuit).

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What is the purpose of the EPCEPC —Echo Protection Circuit in the aircraft DMEDME —Distance Measuring Equipment equipment?