to provide clearances or spaces for ease of mounting as shown or suggested by the gaps 32 34 between the lateral members 16 18 and 20 22 respectively it is also an important feature of the invention that each of the modular components c 1 c 2 c 3 be a fully self contained standalone component that is fully operational independent of any of the other modular components mounted on the rack therefore notwithstanding their substantially reduced sizes each of the modular components c 1 c 2 c 3 must have independent input and output ports a power supply and any other input and output ports needed for operation within the overall system referring to fig3 for example the rack shelf 12 when used in a satellite communication system may include two block upconverters bucs a b and a redundant switchover unit rsu 38 the units a b and 38 are shown to be approximately one third each of the overall width w 19 inches of the shelf 12 the heights of the modular components a b 38 are all equal to one rack unit ru as may be standard for the industry or for the modules being used referring also to fig4 the arrangement.