All you need is a phone line! All phone lines have a constant flow of voltage, around 40-70 volts (up to 100 volts when it rings!), but you can't just plug stuff into it and expect it to work.
Children older than 5 and more than 40 pounds must ride in a booster seat until the child is 8 years old or is taller than 4 feet 9 inches. Anyone over the age of 8 must be protected by a safety belt.
Booster seats are generally for children weighing 40 to 120 lbs. Boosters should be used until a child is at least 57 inches tall, the minimum height at which a car's seat belts will fit him or her appropriately, typically between the ages of 8 and 12 years.