Rabizo;
I'm not at my PC at the moment but IIRC it's the GCI object (Ground Control Intercept). We've used it in our Battle of Britain campaign to simulate the British radar.
Essentially you'll get a text message on-screen about the grid, altitude and bearing to the enemy formation from your aircraft's location.
There's also a Ground Observer object in C&C which is similar but less range and gives you aircraft type/direction they are flying IIRC.
It's a very handy tool and provides some immersive realism.
There's also a Shore? (or Ship) Observer (not sure of title) C&C object which acts like the island-spotters in the Pacific and provides info on ships which pass within range. Cool for Pacific island missions and campaigns.
This is all assuming you have BAT or the C&C mod installed on your non-BAT game (i.e. we use it with HSFX). The C&C Mod can be switched on/off via JSGME and essentially adds a bunch of objects within your FMB that when added to your map will activate the particular function. NOTE: not all the C&C objects work (with HSFX). The ones I mention here work fine online (if all others also have C&C activated) or single player but certain ones such as the Air Sea Rescue object lock up HSFX (but work fine in BAT).
If you click on this link you'll see some pics of the 'flak barrage' object with C&C. One object providing a 1 x 1 km of flak.
Click on Operations then Theater of Operations then Sqn Mission Photos.
https://381st.nfshost.com/