In
electronics, a
detector is an older term for an
electronic component in a
radio receiver that recovers
information contained in a
modulated radio wave. The term dates from the first three decades of radio (1886-1916). Unlike modern radio stations which transmit sound (an
audio signal) on the radio
carrier wave, the first radio transmitters transmitted information by
wireless telegraphy, using different length pulses of radio waves to spell out text messages in
Morse code. So early radio receivers did not have to extract a sound wave from the incoming radio signal, but only "detect" the presence or absence of the radio signal, to produce clicks in the receiver's earphones representing the Morse code symbols. The device that did this was called a detector. A variety of different detector devices, such as the
coherer,
electrolytic detector, and
magnetic detector, were used during the wireless telegraphy era.