Doorbells and other conventional electric bells have an electric circuit mechanism that consists of a switch, electromagnet, clapper and bell. Electricity flows when someone pushes the switch, causing the electromagnet to generate a magnetic field that pulls the clapper towards the bell to make it ring.
Common types of electric bells include the bell, buzzer and chime. The bell and buzzer mainly differ in the sound apparatuses they use, but both use their clappers for their self-interrupting circuit designs. As the powered electromagnet pulls the clapper, the clapper's contact arm moves away from the contact metal and opens the circuit. The electromagnet loses its magnetism, which causes the contact arm to link back with the contact metal and close the circuit. The electromagnet becomes magnetized again, repeating the process until the switch is released.
The chime makes use of a solenoid, which is a special type of electromagnet that has a piston or metal cylinder surrounded by the coil of wire. This piston acts like a clapper and slides backward or forward depending on the magnetic state of the electromagnet. In common designs, the piston moves and hits a tone bar that produces the chime. Other designs use extra tone bars, solenoids and buttons to produce more chimes.