A communication controlling apparatus, which is connected to a telephone line and a serial bus, comprises a mapping table, which brings a fixed address, which a terminal device possesses, into correspondence with a node ID assigned to a terminal device connected to the current serial bus. The message indicates that the user at the moveable barrier operator requires assistance. The first and second locking portions are selectively rotatable between a released position and a locked position. The second power switch allows selective connection of a first bus to a corresponding location between adjacent DC voltage sources.