This device patented by a German scientist, Ferdinand Braun, in 1899 was made of a single metal wire, fondly called a cat's whisker, touching against a semiconductor crystal.
So little wonder that at the time of the broadcast only about 200 receiving licences had been sold, although it is possible that many more tuned in on homemade crystal "cat's whisker" sets.
To create the point-contact transistor, Shockley's team modified the cat's whisker by placing two fine metal wires close together on the surface of a germanium crystal, turning it from a diode into a triode.