INTERROGATOR- The ground-based surveillance  radar beacon transmitter-receiver, which normally  scans in synchronism with a primary radar,  transmitting discrete radio signals which repetitious- ly request all transponders on the mode being used to  reply. The replies received are mixed with the  primary radar returns and displayed on the same plan  position indicator (radar scope). Also, applied to the  airborne element of the TACAN/DME system.  (See TRANSPONDER.)  (Refer to AIM.)  INTERSECTING RUNWAYS- Two or more  runways which cross or meet within their lengths.  (See INTERSECTION.)  a.  A point defined by any combination of courses,  radials, or bearings of two or more navigational aids.  b.  Used to describe the point where two runways,  a runway and a taxiway, or two taxiways cross or  meet.  INTERSECTION DEPARTURE- A departure from  any runway intersection except the end of the runway.  (See INTERSECTION.)  INTERSECTION TAKEOFF- (See INTERSECTION DEPARTURE.)  IR- (See IFR MILITARY TRAINING ROUTES.)  IRREGULAR SURFACE- A surface that is open for  use but not per regulations.  ISR- (See INCREASED SEPARATION REQUIRED.)  INTERSECTION- 8/15/19 7/16/20  Pilot/Controller Glossary Pilot/Controller Glossary  PCG I-6 