Doorbells consist of three basic parts: a transformer that takes a home's 120 volt power and converts it between 10 and 15 volts; a chime box that actually produces the audible signal when someone rings the doorbell; and doorbell buttons that, when pressed, complete the circuit and make the chime sound. Connecting them all together is a task most homeowners can take on themselves.
The chime box should be mounted in a central location in the house so the doorbell is heard easily throughout the home. Make a small hole where the chime box will be located and feed the doorbell wires through the opening. Doorbell units use thin 18-gauge bell wire to make connections. String bell wire through walls and to the doorbell buttons and transformer or along door frames and baseboards if access to the space between walls is prohibited.
Making the Connections
Connect a wire to the chime box on one end and to one of the doorbell buttons on the other end. A second wire connects to the other screw on the doorbell button and to the "hot" or powered terminal on the transformer.
Connect a third wire, usually a white wire, to the neutral terminal on the chime box and to the neutral terminal on the transformer.
If your doorbell has more than one tone, it will have a third terminal on the chime box. Add a second doorbell button by connecting a wire from the second button to the third terminal on the chime box and another wire from the other screw on the second button to the hot terminal on the transformer.
Powering the Transformer
Transformers are usually mounted on a floor joist in the basement adjacent to a junction box that is not crowded with connections. Since you will be connecting into a live electrical circuit, now is the time to kill the power at the breaker box.
Connect the black lead from the transformer to the black wire inside the junction box and connect the white lead from the transformer to the white wires inside the junction box. Secure your connections with wire nuts and make sure the wires into and out of the junction box are secured with insulated staples.
Turn the power back on and test the doorbell.