In the 20th Century the role of electronic gadgetry in covert operations has steadily increased. Each new technological advance in the fields of radio transmission, magnetic fields, miniaturization, sound detection, etc., has offered corresponding opportunity for application in the secret world. Security agencies have had to devote increasing amounts of manpower and resources to keeping up with the often-ingenious electronic devices that have become available.
With the aid of the proper equipment it is possible to listen in on phone conversations, to learn what phone numbers are being dialed from a tapped phone, to eavesdrop on conversations between two people in a park hundreds of yards away, to listen through glass windows into an apartment across the street, or to detect, intercept, and locate radio signals. Gadgetry of this sort is so sophisticated that many US embassies have a special protected room where all top secret conversations are held.
Corresponding equipment has been developed to detect when enemy listening devices are deployed and to otherwise protect communications. Important rooms are periodically “swept” so that hidden bugs can be removed.
The top secret red phones on important Washington desks have no dials or buttons and are listed in no directory. They are connected through specially protected cables and an operator makes your calls. The hot line between Washington and Moscow is similarly protected and even the location of the cable is considered an important secret.
Deploying electronic gadgetry is normally a task for specialists. For example, in the British counter-intelligence agency, still known by its previous name MI-5, staffers known as “listeners” are responsible for bugging and other electronic eavesdropping. They and their counterparts may listen to hours of meaningless talk to gain a few minutes of valuable information. The counterparts to the listeners, the “sweepers”, are responsible for keeping government communications secure.
Outside of the home country, however, the specialists are usually not available and the agents in the field must themselves insert the proper gadgetry. In many cases, the successful deployment of a device requires some covert action. For example, special mirrors can be placed inside a room or on a window within line of sight of a continuous wave radar or infrared/laser beam microphone. Vibrations of the mirror by voices can be collected and at least partially translated into words.
The importance of electronic eavesdropping on enemy conversations and the electronic protection of your own words cannot be overestimated. From enemy communications you can learn what agents are up to, who they are in contact with, the purpose of the plan underway, and obtain leads to other activities. By studying a group under surveillance, their procedures can be identified and their activities elsewhere may be easier to detect.