There are two primary types of wiring in a house: high voltage and low voltage. Electrical contractors almost exclusively install the high-voltage systems that provide electricity for lighting and appliances. Another specialty contractor usually installs low-voltage systems, which serve security, entertainment, communications, environmental control and other functions. High and low voltage wiring systems operate from separate central or service panels, the hubs at the service drop that contain the connection from the utilities and control the distribution of electricity in the house.