Usually the external sensors are connected with a cable each for internal junction box. Here are two or three floors, small cables must be fed through the wall. If this is not possible, the "Single Cable Kit" help. Here a surface-mounting junction box is used to collect all the cables of the sensors, a cable door in the House.
The single cable Kit does not contain any cables. You need a cable from the junction box for the display unit inside! Required is a normal 8-wire cable, an Ethernet cable will do just fine.