Just like they did it in the early 1900's... Galena touched gently with a cat's whisker..  You have to play with it a little to get a clear signal...  Neat thing about this crystal... Reverse it and it  works the same... Can't do that with a 1n34A!  You can still get the real  thing, but the price has gone up since I bought this over 15 years ago...You can fine these at antique electronics.   It goes to show you the a Junk box is a treasure chest!