a gate printer. In addition, TDLS will emulate the  Flight Data Input/Output (FDIO) information within  the control tower.  TERMINAL RADAR SERVICE AREA- Airspace  surrounding designated airports wherein ATC  provides radar vectoring, sequencing, and separation  on a full-time basis for all IFR and participating VFR  aircraft. The AIM contains an explanation of TRSA.  TRSAs are depicted on VFR aeronautical charts.  Pilot participation is urged but is not mandatory.  TERMINAL VFR RADAR SERVICE- A national  program instituted to extend the terminal radar  services provided instrument flight rules (IFR)  aircraft to visual flight rules (VFR) aircraft. The  program is divided into four types service referred to  as basic radar service, terminal radar service area  (TRSA) service, Class B service and Class C service.  The type of service provided at a particular location  is contained in the Chart Supplement U.S.  a.  Basic Radar Service- These services are  provided for VFR aircraft by all commissioned  terminal radar facilities. Basic radar service includes  safety alerts, traffic advisories, limited radar  vectoring when requested by the pilot, and  sequencing at locations where procedures have been  established for this purpose and/or when covered by  a letter of agreement. The purpose of this service is to  adjust the flow of arriving IFR and VFR aircraft into  the traffic pattern in a safe and orderly manner and to  provide traffic advisories to departing VFR aircraft.  b.  TRSA Service- This service provides, in  addition to basic radar service, sequencing of all IFR  and participating VFR aircraft to the primary airport  and separation between all participating VFR  aircraft. The purpose of this service is to provide  separation between all participating VFR aircraft and  all IFR aircraft operating within the area defined as a  TRSA.  c.  Class C Service- This service provides, in  addition to basic radar service, approved separation  between IFR and VFR aircraft, and sequencing of  VFR aircraft, and sequencing of VFR arrivals to the  primary airport.  d.  Class B Service- This service provides, in  addition to basic radar service, approved separation  THRESHOLD- The beginning of that portion of the  runway usable for landing.  (See AIRPORT LIGHTING.)  (See DISPLACED THRESHOLD.)  (See OVERHEAD MANEUVER.)  360 OVERHEAD - THREE-HOUR TARMAC RULE– Rule that relates  to Department of Transportation (DOT) requirements  placed on airlines when tarmac delays are anticipated  to reach 3 hours.  THAT IS CORRECT- The understanding you have  is right.  THA- (See TRANSITIONAL HAZARD AREA.)  TF - (See TERRAIN FOLLOWING.)  (See SEGMENTED CIRCLE.)  (Refer to AIM.)  TETRAHEDRON- A device normally located on  uncontrolled airports and used as a landing direction  indicator. The small end of a tetrahedron points in the  direction of landing. At controlled airports, the  tetrahedron, if installed, should be disregarded  because tower instructions supersede the indicator.  TERRAIN FOLLOWING- The flight of a military  aircraft maintaining a constant AGL altitude above  the terrain or the highest obstruction. The altitude of  the aircraft will constantly change with the varying  terrain and/or obstruction.  TERRAIN AWARENESS WARNING SYSTEM  (TAWS)- An on-board, terrain proximity alerting  system providing the aircrew ‘Low Altitude  warnings' to allow immediate pilot action.  TERMINAL-VERY HIGH FREQUENCY OMNI- DIRECTIONAL RANGE STATION (TVOR)- A  very high frequency terminal omnirange station  located on or near an airport and used as an approach  aid.  (See NAVIGATIONAL AID.)  (See VOR.)  of aircraft based on IFR, VFR, and/or weight, and  sequencing of VFR arrivals to the primary airport(s).  (See CONTROLLED AIRSPACE.)  (See TERMINAL RADAR SERVICE AREA.)  (Refer to AIM.)  (Refer to CHART SUPPLEMENT U.S.)  Pilot/Controller Glossary Pilot/Controller Glossary  8/15/19 12/31/20  PCG T-3 