Apparatus for the transmission of images; apparatus for the transmission of sound; apparatus for the transmission of sound or images; apparatus for use in digital communication transmission; apparatus for use in high-frequency transmission; appliances for the transmission of messages; cables for optical signal transmission; cables for signal transmission systems; carrier transmission apparatus; carriers for message transmission; data transmission networks; digital data transmission apparatus; digital optical transmission apparatus; digital optical transmission instruments; wall plates adapted for electrical components; wall plates for electrical components; wall plates for electrical connections; connections for electric cables; connections for electric lines; connections for use with optical fibre cables; connections for use with optical fibres; plug connections (electric); plug-in connections (electric)