Apparatus for use in audio-visual communication; racks and mountings specifically adapted for use with audio, visual, computer and telecommunications equipment; computer networking apparatus; audio and video receivers; digital video adaptors for use with computers; audio cable; audio cable connectors; cable for electrical transmission; data security instruments; data logging apparatus; uninterruptible power supply apparatus (battery); data switching apparatus; data transfer apparatus; data transmission cables; wire free data transmission apparatus; apparatus for use in audio-visual communication; electric leads; cables for signal transmission systems; cases adapted for television display apparatus; apparatus for linking computers into networks; cabling networks (installations) incorporating fibre optic cables; communications cables; computer cables; fibre optic cables; telecommunications cable; computer software for time control