The principle is similar to that of the moving-magnet except that a stationary magnet induces a field into an armature which is moved by the cantilever. It was a useful alternative when a magnet could add appreciable mass to the cantilever. Lightweight magnetic materials have now overcome this snag, so the induced magnet is less attractive.
"I want to thank you for all the effort you made to resurrect my father's voice from that 8-track. You did an admirable job."