Detector (radio)
A detector is a device that recovers information of interest contained in a modulated wave. The term dates from the early days of radio when all transmissions were in Morse code, and it was only necessary to detect the presence (or absence) of a radio wave using a device such as a coherer without necessarily making it audible. A more up-to-date term is demodulator, but "detector" has a history of many decades of use, even if it is a misnomer.
Read more about Detector (radio): Frequency and Phase Modulation Detectors, Phase-locked Loop Detector