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.
Group 2: for children weighing 15 - 25 kgs (33 - 55 lbs), roughly 4 to 6 years. Booster seats that only fit into Group 2 are less common. Most are group 2 and 3, or groups 1, 2 and 3. Groups 2 & 3: for children weighing 15 - 36 kg (33 - 79 lbs), roughly 4 to 11 years.