Electric bell mechanism, diagram. The bell push is a switch (upper left) which completes the circuit, and switches on the electromagnet (grey, with coils). The soft iron armature (blue) to which a small hammer is attached, is attracted to the electromagnet and the hammer strikes the bell (green). This breaks the circuit and the electromagnet switches off. The armature returns to its original position and the cycle repeats as long as the bell push is pressed.