Which communication system is designed specifically for interoperability among different military branches?

The Joint Tactical Radio System (JTRS) is the correct answer because it was developed specifically to ensure seamless communication across different military branches. JTRS is a key component of the U.S. Department of Defense's efforts to achieve joint interoperability, allowing various branches, such as the Army, Navy, Air Force, and Marine Corps, to communicate effectively despite using different systems and equipment.

The JTRS encompasses a family of software-defined radios that can adapt to varying communication needs and frequencies, enabling real-time voice, data, and video exchanges. This flexibility ensures that operational forces can coordinate more efficiently, share critical information on the battlefield, and respond to dynamic military conditions.

In contrast, the other options represent different types of communication systems that do not focus on interoperability between military branches or are not designed for military applications. The Public Address System, for example, is primarily used for announcing information in public spaces and lacks the robust capabilities required for tactical military communication. Meanwhile, Citizen Band Radio (CB) is intended for personal use and communication among civilians, lacking secure military functionality. The Ground-based Tactical Link may serve specific communication functions but does not possess the broad interoperability and adaptability features of JTRS.