Figure 14-42.  Light gun signals.  Figure 14-43.  Transponder phraseology.  provides all the same information the ATCRBS, but will do  so more rapidly and with significantly more accuracy. By  broadcasting aircraft position information to a ground station,  ADS–B can also provide coverage in areas that do not have  radar coverage. In addition, ADS–B provides trajectory  information that includes speed and direction of motion.  information unless an aircraft is equipped with a transponder.  A transponder is also required to operate in certain controlled  airspace as discussed in Chapter 15, “Airspace.”  A transponder code consists of four numbers from 0 to 7  (4,096 possible codes). There are some standard codes or ATC  may issue a four-digit code to an aircraft. When a controller  requests a code or function on the transponder, the word  “squawk” may be used.  Figure 14-43  lists some standard  transponder phraseology. Additional information concerning  transponder operation can be found in the AIM, Chapter 4.  The transponder is the airborne portion of the secondary  surveillance radar system and a system with which a pilot  should be familiar. The ATCRBS cannot display the secondary  14-25  Transponder  Color and Type of Signal  Movement of Vehicles,  Equipment and Personnel  Aircraft on the Ground  Aircraft in Flight  Steady green  Flashing green  Steady red  Flashing red  Flashing white  Alternating red and green  Cleared to cross,  proceed or go  Not applicable  Stop  Clear the taxiway/runway  Return to starting point on airport  Exercise extreme caution!!!!  Cleared for takeoff  Cleared for taxi  Stop  Taxi clear of the runway  in use  Return to starting point  on airport  Exercise extreme caution!!!!  Cleared to land  Return for landing (to be followed  by steady green at the proper time)  Give way to other aircraft and  continue circling  Airport unsafe, do not land  Not applicable  Exercise extreme caution!!!!  Radar Beacon Phraseology  SQUAWK (number)  IDENT  SQUAWK (number) and IDENT  SQUAWK Standby  SQUAWK Low/Normal  SQUAWK Altitude  STOP Altitude SQUAWK  STOP SQUAWK (mode in use)  STOP SQUAWK  SQUAWK Mayday  SQUAWK VFR  Operate radar beacon transponder on designated code in MODE A/3.  Engage the “IDENT” feature (military I/P) of the transponder.  Operate transponder on specified code in MODE A/3 and engage the “IDENT”  (military I/P) feature.  Switch transponder to standby position.  Operate transponder on low or normal sensitivity as specified. Transponder is  operated in “NORMAL” position unless ATC specifies “LOW” (“ON” is used instead of  “NORMAL” as a master control label on some types of transponders).  Activate MODE C with automatic altitude reporting.  Turn off altitude reporting switch and continue transmitting MODE C framing pulses.  If your equipment does not have this capability, turn off MODE C.  Switch off specified mode. (Used for military aircraft when the controller is unaware of  military service requirements for the aircraft to continue operation on another MODE.)  Switch off transponder.  Operate transponder in the emergency position (MODE A Code 7700 for civil  transponder, MODE 3 Code 7700 and emergency feature for military transponder).  Operate radar beacon transponder on Code 1200 in MODE A/3, or other  appropriate VFR code. 