A phonic wheel is a historic electromechanical device consisting of a toothed iron wheel rotated by an electromagnet. The electromagnet is pulsed by a tuning fork circuit, causing the wheel to advance exactly one tooth per vibration. It was originally used to maintain precise synchronous speeds in early multiplex telegraphy and timing instruments.
Heard on the job
The museum's telegraph exhibit features a working phonic wheel to demonstrate early synchronization methods.