These Intelsats are positioned in stationary orbit around the equator and carry tens of thousands of simultaneous phone calls, faxes, and e-mails. These regional communications are monitored by the above stations as well as the following additional monitoring stations. These are located primarily at military bases and embassies throughout the world. These listening posts were especially critical before the advent of satellite communications. Interception of communications flowing through underground or under water cables is easy once the cables surface and connect to microwave towers.
Microwave transmissions move communications in a line of site fashion from tower to tower.
Microwave communications frequently converge at large cities, typically a capital city. In addition to ground-based observation centers, spy satellites and airplanes are also used. They are capable of receiving high frequency radio broadcasts as well as cellular transmissions. Numerous spy satellites are busy acquiring photographs. Although the quality and extent of photo coverage is classified, some photos from the Corona program of the 1960s are being made public.