The farm service is the point of transition from the utility distribution system and the farm wiring system. The main component is a transformer that converts the distribution system voltage (from 4,000 to 25,000 Volts) to the voltages used on the farm (120 and 480 Volts). Higher voltage allows for smaller wires for longer runs and still minimize voltage drop. The farm service is typically located in the center of electrical activity to minimize the length of wires to various farm buildings and other electrical energy users, such as well pumps. The National Electric Code is the minimum standard for farm wiring and connection to the service transformer. It is recommended that farms have one point of service (and one transformer), although in some situations multiple services may be required. The transformer should be located at least 20 feet from farm electrical equipment and other conductive structures such as grain bins or metal buildings. The point of service must be fitted with a single switch that will disconnect the entire farm from the distribution system. This disconnect switch should be clearly identified and visible to employees, utility, and emergency workers. The point of service is also the point at which any permanent or backup energy generation system is connected to the farm/distribution wiring system.