crystal detector

noun, Radio.
1.
a device for rectifying a modulated radio-frequency signal, consisting of a crystal of germanium, silicon, galena, or the like with a cat whisker contact, permitting a high-frequency current to pass freely in one direction only: one of the two principal components of a crystal set.
Origin
1905-10
British Dictionary definitions for crystal detector

crystal detector

noun
1.
(electronics) a demodulator, used esp in microwave circuits and in early radio receivers, consisting of a thin metal wire in point contact with a semiconductor crystal