Beware of double voltage i.e. 220 vac instead of 120vac input ,when connecting separate computer components with USB, Firewire, TV -S connector or sound cables such as a printer, monitor, external hard drive or home theater system. This is especially noteworthy when the remote components are in separate room of the house or across the room and plugged into a separate outlet.
Electrical power is supplied to your house from the utility company with three cables; two power and one common. The power cables are identified as line one and line two. The voltage between line one and common is 120VAC . The same is true for line two at 120VAC. The voltage between line one and line two is 220VAC. The three cables are routed into the circuit breaker box and connected to separate buss bars. The breakers are plugged into the box and make connection to the buss bars for line one and line two. The arraignment of the breakers are alternating between line one and line two.