When you press a doorbell button, you complete an electrical circuit that allows household electricity to flow through the doorbell's internal electromagnet. The magnetic field generated by the electromagnet is then used to power a mechanism that creates the doorbell sound. Doorbells are low-voltage devices.You don't have to turn the power off for this because, unlike most systems in your home, the power is stepped down by the doorbell to a safe 16 or even 12 volts (V) with very few amps. ... Basically, your doorbell is an open circuit that closes when you push the button.