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 frequencies. 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.