A Virtual Entrance/Exit (or short “VExtern”) in CTC is a point where trains enter or leave your territory not based on a schedule but at random. It has two blocks (“vextern track”) with a name applied to both tracks within the vextern group. Both blocks are at the opposite ends of a stretch of blocks such that a train enters one at one side and leaves on other side for a complete travel. There are no switches on that path.
These tracks are considered a property of a “foreign company”. The only interaction with your territory is the crossing (diamonds) with “your” tracks. Each vextern track has a number indicating how many trains are generated within a 24-hour period coming in on this track.
Since you’re not in charge of the trains on the foreign road, no triangles are shown indicating which direction a train is allowed to pass. Except for the routes needed to pass the diamonds (including signaling) there is nothing for you to do for these trains, and communications to such trains are limited to tell the drivers to be patient.