The Radar Signal Detecting Set AN/APR-39A(A)1 provides the pilot with visual and audible warning when a hostile fire-control threat is encountered. Antenna-detectors provide frequency coverage into the millimeter-wave region of the RF spectrum, identifying radar sources using an Emitter Identification Data (EID) module located in the processor. The processor is software controlled, and updates to the EID can be installed with minimum effort. Search radars and fire control radars operating in search mode are shown as strobes at edge of Indicator Display. Search is defined here as a signal that has not yet been identified. Once identified, search radar strobes are replaced by a generic symbol denoting threat type. The symbol is modified to show changing threat status (new threat, acquiring, tracking, launch). Intercepted signals that do not match specific threat parameters in the EID are displayed as unknowns (Symbol U). Threats are displayed on the Indicator at their relative bearing from the aircraft. Synthetic voice messages give threat location to the nearest clock position over the aircraft ICS so that evasive maneuvers can be initiated. The AN/AVR-2 Laser Warning Receiver interfaces with the AN/APR-39A(V)1 providing early warning against laser threats.

Will automatically return to normal when signal density in the environment decreases. The synthetic voice message "THREAT DETECTION RESTORED" will occur.