1. an absence of or abstention from radio transmission: "at midnight, the enemy went on total radio silence"
▪ absence of communication from a person or group from whom communication might have been expected:"the long radio silence has been due to the intensity of parenting an infant"
In telecommunications, radio silence or emissions control (EMCON) is a status in which all fixed or mobile radio stations in an area are asked to stop transmitting for safety or security reasons. Wikipedia