Wireless doorbells have been used in homes since the 1990s. They are replacing wired doorbells, which are built into the electrical system of a home. A wireless doorbell can be placed anywhere, and they are affordable and easy to install. Radio waves connect the transmitter to the bell, so physical wiring and electrical work is unnecessary. There are many different types of wireless doorbells on the market, and they come in different sizes, ranges and sounds.