Please note:these doublers are sold as single units not pairs. Our Port Doublers allow two devices to be connected using only one port of a structured cabling system. The CAT5/5e/6 cable used in a conventional Fast Ethernet network is made up of 8 conductors, 4 of which are unused. The port doubler makes use of these 4 spare conductors, to provide a second connection over a single cable run, without any loss of performance. Port Doublers must be used in pairs by connecting one to the patch panel and the other to the wall outlet.