Communications security is the discipline of preventing unauthorized interceptors from accessing telecommunications in an intelligible form, while still delivering content to the intended recipients.
PRC-77 VHF radio with digital voice encryption device
Military communications or military signals involve all aspects of communications, or conveyance of information, by armed forces. Examples from Jane's Military Communications include text, audio, facsimile, tactical ground-based communications, naval signalling, terrestrial microwave, tropospheric scatter, satellite communications systems and equipment, surveillance and signal analysis, security, direction finding and jamming. The most urgent purposes are to communicate information to commanders and orders from them.
United States Army Signal Corps switchboard operators in the 1940s
A Japanese courier pursued by Cossacks during the Russo-Japanese War, 1904
WRNS signalwomen training naval signalling, 1943
A Luftwaffe officer using a radio kit on a Panzer III, 1940