The first sounding through the radio wave was carried out in the station established in Guglielmo Marconi in Cornwall in 1902 so that the Eastern Telegraph company could easily work. During the First World War, opposing armed forces formed special units to listen to each other’s radio signals. The real improvement in the listening devices is the giant dimensions of transistor and laser. The first transistoric little spy listeners were made in the 1950s. These listeners, who work on Pille, have about a hundred meters of range. The ashtray could easily be placed into small vehicles such as a cigarette box and a pen. The phone listening devices, this area has opened a new era. The only thing to do after the spy listener is placed on the phone’s handset is to dial the phone number from wherever the listener is placed.
In the 1970s, the laser lasers sent to any window brought the voices in the room back to the source of heat, because the spy tool would be activated when the number was dialed, but the caller would not hear anything. The more dirty the glass was, the easier it was for the spies. Because dirty glasses make it easier for the laser beams to break and return. Share Information