This newest design NEMA 14-30 Y splitter features a built-in selection switch so it’s impossible to accidentally overload your circuit by running both appliances at once. This is the safest design. Now you can leave your car charger and electric dryer plugged in at the same time, and not worry about tripping your breaker, thanks to the built-in switch! This gives you greater convenience and peace of mind, and reduces wear on the electrical outlet from repeated plugging in and unplugging.