This page contains diagrams to add a new electrical outlet to an existing circuit. Arrangements are included to use an existing receptacle circuit or lights and switch circuits as the source for a new wall outlet.
This is an updated diagram for the same circuit. Here the source neutral, known as a grounded neutral, is run through to the switch box where it can be used to power switches that require a neutral connection. A neutral connection like this is now required in most new switch boxes as of the code changes in 2011.
This diagram illustrates wiring for a circuit breaker with a built-in ground fault circuit interrupter. This 20 amp ground fault interrupter breaker is a form of gfci that can be installed at the circuit source. This kind of circuit is used for dishwashers, whirlpool spas and other locations where water contact is likely.
A doorbell circuit for two or more doors will have a separate contact on the chimes for each button included. At the chimes, one wire from each button is spliced to the output wire on the transformer. The second wire is connected to one of the contact screws on the chimes.