- When you think of a doorbell, the first sound that may come to mind is the chime or buzz that sounds when a visitor arrives at the door. To create this sound, electric doorbells employ electrically powered buzzers or chimes that create sound when exposed to electricity. In systems that use a chime, electricity passes through a metal coil wound tightly inside the chime's housing. As the electricity passes through the coil, according to the online science center, the MadSci Network, it creates a magnetic field. This magnetic field affects a nearby metal rod that bends inward toward the coil's magnetic pull and strikes a tubular chime to create a vibration; this vibration travels through the air, allowing the human ear to interpret it as sound. Depending on the model of chime, the device may employ two magnetic coils that pull the rod in opposite directions, first striking one chime and then traveling the opposite direction to strike another.
- Although many individuals may associate the traditional chime with an electric doorbell, some doorbells use buzzers instead of magnetic or electronic chimes. In systems that use buzzers, electricity flows through a piezo-electric disk when a visitor pushes the outside doorbell button. When the alternating current of household electricity passes through the disk, it causes a thin membrane to vibrate. This vibration, like the vibrations produced by the traditional chimes, travels through the air and arrives in the owner's ear as a buzzing sound. Depending on the amount of electrical current supplied to the buzzer, the condition of the membrane and variations in the electrical flow, the buzzer may sound at a high pitch, low pitch or any combination of musical notes.
- Whether a doorbell uses chimes or an electric buzzer, it must supply electricity to the device in order to create sound. According to the "New England Breeze," a publication that provides energy-saving tips to New Englanders, most modern household doorbells operate on 24-volt alternating current electricity. Since household electrical wires typically carry around 110 volts or more, electricians install step-down transformers that convert the high voltage electricity to suitable levels for doorbell use. On one side of the transformer, two wires supply electricity to the doorbell chime or buzzer unit. Another pair of wires protrude from the other side of the transformer; these wires extend through the home's walls to the outside doorbell switch. Under normal conditions, when no visitor exists, the outside switch remains in an "open" condition, preventing delivery of electricity across the circuit to the chime or buzzer unit. When a visitor arrives and presses the outside button, though, metal contacts inside the button close, completing the electrical circuit and allowing electricity to flow to the chime or buzzer unit. Depending on the model of outside switch, it may also use the electricity in the circuit to power a small, low-voltage light that indicates the button's presence to visitors.
