Inventor H. Christian Berger took a relatively basic scientific principle--that a loud sound can trigger a telephone transmitter to send an electric current through an electromagnet--and harnessed it for perhaps the most noble purpose of all: fun.
Berger created several toys that responded to sound, using the electric current from the telephone transmitter to trip a spring or lever. For example, this wooden pup is shoved out of his kennel by a spring at the sound of a handclap, making him appear to jump at your beck and call.
The same principle applies to a bank that uses a lever to flip a coin inside when you clap your hands, and a dummy that dances when you whistle into the transmitter attached to the box he stands on.
Read the full story in Toys That Obey Your Voice.