this remote-controlled toy car, made by Masudaya in the 1950s, is illegal to operate! read on to learn why... 
take a look at this component inside on the right. it's not a fuse...
it's called a coherer. it's a tube filled with metal filings. when an RF signal is applied, the filings cling together and the resistance drops dramatically. this turns on a motor that cycles the operating mode of the car.
when the motor spins and changes the operating mode, it lifts up that little metal arm and drops it, tapping the coherer to shake the filings apart to reset it.
nothing with the receiver end is illegal, but this transmitter is! it's a spark gap transmitter which emits broad-spectrum RF, interfering with lots of other receivers. they were (for the most part) banned in the late 1920s.
