The neutral wire in this circuit is taken from the receptacle and spliced to the white on the new cable, and to a pigtail that runs back to the receptacle. The hot is spliced to the black cable wire and a pigtail back to hot on the receptacle.
This wiring diagram illustrates wiring a light switch to control an existing receptacle outlet. The source is at the receptacle and a switch loop is added to a new switch. The hot source wire is removed from the receptacle and spliced to the red wire running to the switch. The black wire to the switch connects to the hot on the receptacle.
This page contains several diagrams for wiring a switch to control one or more receptacle outlets including a split receptacle and multiple outlets wired together.
This diagram illustrates the arrangement for a 20 amp double receptacle circuit with a shared neutral wire. This arrangement is typically used in a kitchen where two appliance circuits are needed in close proximity to each other.
The always-hot wire from the receptacle is spliced to the black wire on the fixture cable, and to a pigtail that connects back to the hot terminal on the receptacle. At the light fixture box, the black is spliced to the black from the switch cable. At the switch box the black wire is connected to the bottom terminal on the new switch.
The wiring in this diagram is for adding a new light fixture to a switched receptacle, i.e. one that is hot only when a switch is on. These are commonly used to turn a table or floor lamp on and off from a wall switch.
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.
If, however, you’re putting in a new hardwired doorbell or you need to repair an existing one, the diagrams on this page illustrate the most common installations you will find. Included are wiring for a typical hardwired doorbell, a two-button doorbell, an old house doorbell powered by a battery, and an alternate power source using an ac adapter.