XB5AJ21 2 Position NO Selector Switch. Schneider Electric XB5 series complete selector swithces. The switches are supplied complete with everything needed to install in a panel. The Harmony XB5 range of Key Switches from Schneider Electric brings you reliability and assurance in site safety via the use of a key to control the output to the circuit. The device is suitable for industrial controls where safety is paramount, especially in areas where hazardous machinery needs accountable operation.