intelligence activities concerned with identifying and counteracting the threat to security posed by hostile intelligence organizations or by individuals engaged in espionage or sabotage or subversion or terrorism
electronic equipment that converts sound into electrical signals that can be transmitted over distances and then converts received signals back into sounds; "I talked to him on the telephone"
the discipline that studies the principles of transmiting information and the methods by which it is delivered (as print or radio or television etc.); "communications is his major field of study"