Oxford Electric Bell

[1][2] It is located in a corridor adjacent to the foyer of the Clarendon Laboratory at the University of Oxford, England, and is still ringing every half second, albeit inaudibly due to being behind two layers of glass.

The clapper is a metal sphere approximately 4 mm (3⁄16 in) in diameter suspended between the piles, which rings the bells alternately due to electrostatic forces.

The use of electrostatic forces means that while high voltage is required to create motion, only a tiny amount of charge is carried from one bell to the other.

The bell will eventually stop when the dry piles have distributed their charges equally if the clapper does not wear out first.

[2] Apart from occasional short interruptions caused by high humidity, the bell has rung continuously since 1840.