ServSwitch Serial Flash Kit ServSwitch Serial Flash Kit Flash upgrade your ServSwitch, ServSwitch Ultra, Matrix ServSwitch, or ServSwitch Affinity firmware via the RJ-11 serial port. Connect the RJ-11 serial port on the back of your ServSwitch to a DB9 serial PC port. Includes an RJ-11-to-DB9 adapter and a 10-foot (3-m) RJ-11 (6-wire) straight-through cable.