Low voltage power is described as power supplied from a transformer of 30 volts or less. The transformer actually steps down and converts 120-volt power to 30 volts or less.
Transformers are normally mounted on a junction box. Sometimes transformers have more than one voltage connection point, called a multi-tap transformer.
Transformers are constructed of two tightly wound coils encased in a metal cover. Since the two coils are placed closely together in the case, current flows through the primary winding (the 120-volt side) and as it does this, it produces a magnetic flow. This flow produces current in the second coil winding (secondary winding) that produces the low voltage output.
The primary coil has more windings than the secondary coil. Because of the reduced number of windings in the secondary coil, the voltage output is much less. Secondary windings usually produce voltages between 8 and 24 volts.
Some of the more common transformers used in homes are those used to feed furnaces and doorbells. Furnaces use the low voltage through a thermostat to turn the furnace on and off. a doorbell uses the power to run to a switch outside the door of your home to complete a circuit to the doorbell chime.