Abstract: The technology of this application is generally directed to a method for temporary installation of a third military transponder while maintaining an existing dual civil transponder architecture. In one example embodiment, coax relays are installed between one of the civil transponders, the corresponding antennas, and the military transponder. A switch is installed to drive the coax relays and determine which transponder (e.g., civil or military) is connected to the antennas. The circuit breaker of the transponder not being used at the time can be pulled and collared to remove power to the equipment, and a software configuration loader card is used to configure the avionics.