Name one type of secure voice communications system used in the Air Force.

The Secure Telephone Unit (STU) is a type of secure voice communications system utilized by the Air Force to ensure confidential communication. The STU is designed to provide secure, encrypted voice communication over regular telephone lines, making it suitable for military operations where security is paramount. Its encryption capabilities allow personnel to transmit sensitive information without the risk of it being intercepted or compromised by unauthorized entities.

The STU's design reflects the need for secure communication in various operational environments, ensuring that commanders and personnel can communicate critical information securely and effectively. This makes it an essential tool in maintaining operational security and ensuring the integrity of communications within military operations.

Other systems mentioned may have their functions, but the STU's historical significance and reliability as a secure voice communication device set it apart as a critical component in the Air Force's communication strategy.