If a filling station allows customers to pay at the register, the data from the dispensers may be transmitted via RS232, RS485 or Ethernet to the point of sale, usually inside the filling station's building, and fed into the station's cash register operating system. The cash register system gives a limited control over the fuel dispenser, and is usually limited to allowing the clerks to turn the pumps on and off. A separate system is used to monitor the fuel tank's status and quantities of fuel. With sensors directly in the fuel tank, the data is fed to a terminal in the back room, where it can be downloaded or printed out. Sometimes this method is bypassed, with the fuel tank data transmitted directly into an external database.