This video lecture explains Secondary radar system, principle of Secondary radar, its block diagram, Modes and codes of SSR, Advantages & disadvantages of Secondary radar.
We were discussing the transponder code. If you will see the transponder it has four inputs. Each input can have value from 0 to 7. Thus these are called octal.
We should understand that there are two modes used for civil aviation. Mode A will give identity feature whereas Mode C will give aircraft altimeter reading alongwith the identity. The ground system will receive the reply to its interrogation in the form of identity and Pressure readings in Mode C.
2462 is a specific code set in the transponder as suggested by ATC. This will help ATC to determine the target on his radar scope and based on which he or she will provide radar services to this aircraft.
This is an explanation about the reply pulse from the aircraft. The reply is in coded form between pulses and the width of the pulse indicates the Mode of the transponder. After this we have discussed about the special ident feature used by ATC. This is shown by IDENTITY which will help the controller to identify your aircraft as it will blink on his/her radar scope for 20 seconds in different colour.
