• A wave or signal which returns after being reflected. Such a wave or signal must have sufficient magnitude and delay so as to distinguish it from a direct wave or signal. An example is the repetition of a sound after being reflected off a hard surface.
  • The portion of a transmitted radar signal which a scanned object returns to the radar receiver. Also, the visual indication on a radar screen, such as a blip, of such a reflection. Also called radar echo, or return (3).
  • On the screen of a TV or radar receiver, an undesired condition in which duplicate images appear. May be due, for instance, to the simultaneous displaying of a direct signal and a reflected signal. Also called ghosting.
  • A repetition or reflection of a signal within a communications line. For instance, such an echo resulting from impedance mismatches along a telephone line.
  • A signal, other than the original signal, which is transmitted back to a sender. Used, for example, to test network connections. Also, the transmission of such a signal.

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