The Scan Bus mode interacts with the communications on the bus because it reads the attributes of the controllers communicating on the bus. If no communications are occurring on the bus, the Scan Bus mode starts communications to all controllers on the bus. The Scan Bus mode is helpful when there is not an active supervisory controller connected to the bus since it is the supervisory controller that usually starts the communications due to fixed address. The Scan Bus mode is used to read the EOL termination attribute of the controller. The EOL termination attribute is limited to Johnson Controls manufactured products that have a built-in EOL switch. The location of other EOL devices, such as the MS-BACEOL-0 or jumpers, are not detected. See Proper EOL Termination , FIT Menu and Scan Bus Menu for more information.