we have a FDIO (flight data input/output) system, which connects into the NAS (national airspace system, maybe service....)
When a flight takes off, it gets tagged up on the radar scope, which then sends a DM (departure message) to the NAS which starts up the flight plan.
The computer uses the filed airspeed of the airplane to calculate when it should be where at what time. Then each facility on the way in the route of flight gets strips (centers use EURETS, which i don't know what it stands for, or even if thats the correct acronym for it) a half hour before the aircraft is due to arrive.
In the tracon i work at, we get a strip that says, EGF4199 is supposed to be over NASAL310045 at 1450Z. If we don't see the aircraft within a few minutes of that time, and we havn't had any time updates, we start looking.
Now say we are non radar, or for somereason something messes up, we have to manually send out a DM using the FIDO keyboard, which starts the whole cycle.
I hope that made sense...any other questions just ask