A one-way voice link (OWVL) is typically a radio based communication method used by spy networks to communicate with agents in the field typically (but not exclusively) using

shortwave radio Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...

frequencies. Shortwave frequencies were and are generally highly preferred for their long range, as a communications link of 1200 km is easily possible.

VHF Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF ...

and

UHF Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (on ...

frequencies can be used for one-way voice circuits, but are generally not preferred as their range is at best 300 km (on flat terrain). Since the 1970s infrared point-to-point communication systems have been used that offer OWVLs, but the number of users was always limited. This communications system often employs recorders to transmit pre-recorded messages in real time or in burst transmissions, which minimize the time that a spy needs to be on the air. Voice-scrambling systems have been selectively used for this kind of communications circuit since the 1980s, based on operational needs. Since personal computers became cheap and readily available in the 2000s, time compressed voice scrambling for one-way and bi-directional circuits is a practically free technology. OWVLs have existed outside espionage, for example the NICAM transmission system was modified in the UK to allow for an OWVL to BBC mobile units. This OWVL was typically used for sports events, as it was highly flexible.

Historical context

During the mid- to late

Cold War The Cold War is a term commonly used to refer to a period of geopolitical tension between the United States and the Soviet Union and their respective allies, the Western Bloc and the Eastern Bloc. The term '' cold war'' is used because the ...

the

STASI The Ministry for State Security, commonly known as the (),An abbreviation of . was the Intelligence agency, state security service of the East Germany from 1950 to 1990. The Stasi's function was similar to the KGB, serving as a means of maint ...

(the East German intelligence agency) used point-to-point infrared technology for 2-way voice links within the divided city of Berlin. OWVLs were used intermittently. OWVL transmission methods were used during the

Falklands War The Falklands War ( es, link=no, Guerra de las Malvinas) was a ten-week undeclared war between Argentina and the United Kingdom in 1982 over two British dependent territories in the South Atlantic: the Falkland Islands and its territorial de ...

by UK elite forces to provide information about suitable troop landing areas. This fact emerged in the late 1980s when UK veterans of the war were writing their memoirs. Argentina had access to similar technology to communicate with its military, but did not really use it during this conflict.

Historical context

See also