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 tracks (“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 the 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 are crossings (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. Crossing like that can be more than one track of the foreign company, in which case numbers can be tailored such that the majority of their trains come from one direction on one of their tracks, while the other track is used for trains traveling in the opposite direction.
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.