At the service panel, power delivered from outdoors enters the home and is divided into separate branch circuits that carry electricity throughout the house.

Wiring codes or regulations set an upper limit to the allowable voltage drop in a branch circuit.

This may limit the length of a branch circuit.

The big advantage of this scheme is the ability to remove or add a branch circuit without removing voltage from the whole duct.

A fault on a branch circuit will be detected by all breakers upstream of the fault (closer to the source of power).

A multiwire branch circuit has both energized wires of a 120-240V split phase service.

In non-residential applications, a branch circuit is dedicated to the fire alarm system and its constituents.

Such multiwire branch circuits have special rules in the electrical codes to ensure they are safely applied.

In the oldest installations, several branch circuits could share the same neutral wire, which can cause overloads.