The performance of sensor and communication systems can be limited significantly by hostile Electronic Counter Measures (ECM).
These include passive measures such as radar and laser warning receivers, interception, emitter location systems
as well as active measures such as jammers in various roles using different techniques and deception devices.
For the air vehicle crew the ECM gear detects enemy radar emissions and identifies them.
Each type of radar has its own sound: a low beep is a search
darad probing the sky;
higher pitched tones are fire-control radars seeking to acquire a target;
a nightmare falsetto is a locked-on missile-control radar quiding the weapon.
In the UAV with no pilot the ECM gear alarms the UAV computer system.