Be hold
it needs no battery or power source
http://en.wikipedia.org/wiki/Crystal_radio_receiver
http://scitoys.com/scitoys/scitoys/r...o.html#crystal
Be hold
it needs no battery or power source
http://en.wikipedia.org/wiki/Crystal_radio_receiver
http://scitoys.com/scitoys/scitoys/r...o.html#crystal