Non-communications signals

In signals intelligence (SIGINT), non-communications signals are any signals sent out for a purpose other than communicating information. This includes radar emissions and emissions from instrumentation (which provide information, but are not sent out for the purpose of providing information to others).^[1][2][3]

Electronic signals intelligence (ELINT), which came to be studied in great detail after World War II, attempts to detect and analyze enemy non-communications signals.^[3][4] Foreign instrumentation signals intelligence (FISINT) focuses specifically on non-communications signals emitted by instrumentation, including telemetry signals sent between components of a system.^[5]