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.
If a booster seat has a minimum weight limit of 40 pounds, you can't legally put a 30-pound child in it if your state has a proper use clause. If an infant car seat has a maximum height of 30 inches, it would not count as a legally appropriate car seat for a 34-inch long baby.