Articles about Extending a Circuit
How to Extend Electrical Wiring for a Light Switch
Wiring a Light Switch – How to Add Electrical Wiring for a Outlet and a Light Switch and Extending the Electrical Circuit Wiring for an Outlet and Light Switch.
Planning Electrical Circuit Wiring
How to Plan Electrical Circuit Wiring – In a case like this, the first thing I would do is take a voltage check on the cable that you spliced into to see if it does in fact have the power that is needed for the project.