Before the advent of vacuum tubes and transistor technology, early radio devices received signals with the help of the cat’s whisker detector. An early and somewhat unstable electronic component, the detector was an integral part of the crystal radio sets that came into use in the early 1900s. Though obsolete today, the detectors are still manufactured for antique radio hobbyists. The device consists of a thin wire that lightly touches a crystal of a natural semiconducting mineral such as what? Discuss