Which system is known for long-range, two-way voice communication?

The HF Communication System is recognized for its capability to enable long-range, two-way voice communication. This is primarily due to its use of high-frequency radio waves, which can effectively propagate over great distances by reflecting off the ionosphere, allowing for communication beyond the line of sight. This makes HF particularly valuable for military operations, maritime communication, and other scenarios where long-range contact is essential.

In contrast, the UHF Command Radio Set and VHF Radio Set are tailored more for shorter-range communication. UHF waves are more suitable for line-of-sight communication and are often used for air-to-ground and ground-to-air communications. VHF radios operate similarly, with limited range and are typically used for local communications rather than long-distance connections.

Secure Mode, while important for maintaining the confidentiality of communications, does not specify a particular system for long-range voice communication and could pertain to various types of communication lines that may or may not be HF. Thus, the HF Communication System is distinct in its effectiveness for long-range, two-way voice communication.