A 24-volt doorbell system can be a desirable upgrade or replacement for an old doorbell, as well as a good option for new doorbell installations that require a long distance between the doorbell button and the actual chime. Most houses come with low-voltage (16 volt), two-wire doorbells, which do not provide enough power to ring more than one chime or to power a very loud bell for the hard of hearing. Also, if there is a great distance between the door and the chime, say in a large house, more power is required to push the signal all the way to the chime.
Turn off power to the circuit you'll be attaching to the transformer box.
Unscrew the cover from a junction box on the circuit you've turned off, and remove one of the metal knockouts from the side of the junction box that you want to install the transformer on.
Insert the threaded stub of the transformer through the knockout, and secure on the other side with the provided nut.
Join the leads of the transformer to the corresponding-colour leads in the junction box, and secure with wire connectors.
Mount the chime in a convenient place in your home with the provided hardware. Make sure to mount it somewhere where you can run the wire from the chime to the transformer through a wall or dropped ceiling. Remember that you will also have to run wire from the button outside to the chime.
Drill a hole through the doorjamb from the outside, but not all the way through. This will allow you to run wire through the doorjamb to the inside of the nearest wall, where you can then run it along to the chime box.
Attach two 20-gauge transformer wires to the power terminals on the bell, and run the wire to the two corresponding terminals on the transformer. It helps to use two different-coloured wires, so that you can be sure you're running the positive and negative leads on the transformer.
Attach two more wires to the terminals on the chime, and run these to the doorbell button through the hole you've drilled--again, making sure to attach the wires to the proper terminals on the button. Then secure the button to the outside of the doorjamb using the provided hardware, mounting it directly over the hole that conceals the wiring.
Turn on the circuit you've attached the transformer to, and test the bell.
Doorbells often come in kits that will provide the transformer, chime and button.