The LXNAV S7 vario has a rear seat repeater - the S7D. However, the second unit is more than just a repeater display; it has all of the same functionality as the main unit. Front and back units are connected together with a CAN Bus cable carrying both data and power. One of the great features of the S7 is its connectivity to a PDA/Oudie, whereby the PDA/Oudie receives power and data from the vario. (See setup pic below.) With the LXNAV rear seat repeaters you can also drive a second PDA/Oudie using a PDA-CAN box. This small box connects into the CAN Bus cable between the front and rear varios and provides data and power to the second PDA/Oudie.