A split outlet is an ordinary outlet that has the connection tab removed between the two hot terminals. This allows the outlet to have two distinct feeds, one for the top half of the outlet and one for the bottom half. This could allow you to have one half of the outlet hot and the other controlled by a switch to control a desk lamp.
Outlets are fed via a circuit breaker in a circuit breaker panel. Normally, the whole outlet is fed from one circuit breaker, but that may not always be the case. In fact, this is the biggest danger when dealing with split outlets. You see, you may test the top half and turn off the circuit breaker to it. One may assume the outlet is now safe to work on because the power is off, but not so fast! There could be another circuit feeding the bottom half and it could still be hot. Without the insight to check both sides of the outlet, which is an easy miss, you could be in line for an electrical shock!
The National Electrical Code says that these two hot wires must be connected to a double-pole circuit breaker so that when the breaker is shut off, the action will disconnect both circuits. That way, the outlet will be safe to work on. With individual circuit breakers, there is the likelihood of only getting one shut off and leaving the danger of electrical shock. This is another great safety tip and a potential life saver.
