CONTACT SWITCH DEVICE
An electronic switch operated by the tongue of a rat.
The rat stands on a metal floor carrying an alternating current signal of 8,000 cycles per second. When the rat's tongue touches a contact plate, the signal passes through its body into a transistor amplifier, which clips it into a square wave and converts it to trigger pulses. The pulses retrigger a multivibrator that holds a relay closed for as long as the tongue remains in contact. The relay drives external counters, which record every lap of the tongue at rates in excess of 25 per second.
“A true touch responsive switch requires no effort to manipulate, and, in addition, no sensation of its functioning is perceptible to the operating organism.”— Robert A. Boenning, from the specification
And the world did not beat a path to his door.