The KA-57 must have Service Bulletin 3 to function correctly with the Cessna 300A autopilot. SB 3 configures the adapter so that it is compatible with this autopilot with its C395A computer amplifier. The tracer oscillator in the KA-57 must be disabled by removing a circuit jumper as in all KA-57 units used in interconnects with Cessna autopilots.