Mobile file, storage and shelving units, and parts and accessories therefore, namely, shelves or other storage devices, label holders, card holders, carriages consisting of metal structural elements on which storage devices are mounted or move upon, mobile storage and filing systems comprised of a plurality of mobile track-guided storage carriages which are movable together and apart to open-up and close access aisles between the storage carriages, power units and control units for same, anti-tip devices; electronic control and communication system for controlling, monitoring and diagnosing powered mobile storage systems; safety and security systems comprising infra-red optical sensors used on a plurality of spaced-apart movable carriages to detect an object or a person in the open aisle of the shelving system; electrical lighting fixtures