Radio silence

In telecommunications, radio silence is a status in which all fixed or mobile radio stations in an area stop transmitting.

The radio stations include anything capable of transmitting a radio signal. Radio silence generally applies to the military, where any radio transmission may reveal troop positions, either audibly from the sound of talking, or by its use as a homing signal. In extreme scenarios Electronic Silence (EMCON) may also be put into place as a defence against interception. — Wikipedia