If the two solenoid coils are rigidly connected together, and the solenoids are rigidly connected, one to a hammer lever and the other to an anvil lever, as the currents in the coils produce a sympathetic magnetic field the solenoids are drawn together with the force of the two magnetic fields. On the other half cycle of the supply the two solenoids are repelled from each other with the force again of the two magnetic fields.
