Signals Intelligence
is the interception of electronic emissions of all types to gather information
on a target. This can include listening in on enemy radio conversations (which
may require code-breaking or other cyptological expertise), or monitoring enemy
radar sites. Although most people think of codebreaking when it comes to Signals
Intelligence, even radio signals that do not carry human messages, such as a radar
signal, can reveal a great deal about an enemy. For instance, detecting radar
signals can supply valuable information about enemy positions and strength.
SIGINT has recently taken to outer space, as the U.S. has utilized geosynchronous
satellites for signal intelligence work since the 1960s.
