Which component is used to select SIF reply codes for Modes 1, 2, and 3/A?

The correct choice is the C-7383/APX-76(V) control box, which is used to select SIF (Selective Identification Feature) reply codes for Modes 1, 2, and 3/A. This control box effectively interfaces with the transponder to configure it for the appropriate identification modes used in radar systems for aircraft.

Understanding the function of the C-7383/APX-76(V) control box is crucial because it directly allows the technician to input and modify the SIF codes required for even identifying friend or foe (IFF) in various flight missions. This capability ensures that the aircraft can be positively identified by ground control and other air traffic, enhancing operational safety.

The other components, while essential for various functions in the avionics system, do not manage the selection of SIF reply codes. For example, the Transponder Test Set TS-1843/APX is primarily used for testing and verifying the functionality of transponder systems rather than selecting the specific codes themselves. The Electronic Synchronizer SN-416/APX-76(V) plays a role in synchronizing the systems but does not interact with code selection directly. The Receiver/Transmitter RT-1157/APX-100 is involved in transmission and reception processes