The 01-5940 brake switch is compatible with the RC3 Controller, it has a 2.5mm phone connector for modern BionX systems.
It requires the 01-5993 Brake Switch Adhesive Support (included), and #01-1734 Magnet assembly with adhesive tape
or the #01-1288 Magnet
Cable length: 175mm
Please see this helpful video on brake switch installation.