CTIVO TS MODE AND SKIPMODE CODE
CTIVO TS MODE AND SKIPMODE PLUS

It includes selective addressing, data frames, message types, and much longer messages (56 bits). Mode S is almost a completely different system. (TCAS only sends mode C pulses since it doesn't care about squawk codes.)

Likewise, every 'mode C' radar always sends both types of pulses and internally combines the two responses, so it looks like a single system.

In practice, though, every mode C radar and transponder is also capable of mode 3/A.

CTIVO TS MODE AND SKIPMODE CODE

Note that mode C does not include a squawk code it is only the altitude. The response is a 12-bit redundant encoding of the pressure altitude between -1200 and +126700 feet, in 100 foot increments. If you send a mode C pulse, you get a mode C reply (or nothing).

CTIVO TS MODE AND SKIPMODE PLUS

The response is a 12-bit number called the squawk code, which is conventionally written as four octal digits, plus an optional ident bit. If you send a mode 3/A pulse, you get a mode 3/A reply (or nothing). Modes 3/A and C are very similar, but the interrogation pulses are timed differently and the responses mean different things. So, is Mode S a variation within the Mode 3 'protocol' or is it a stand-alone mode outside of the five IFF modes? I have, however, never seen Mode S referred to as Mode 3/S. I extrapolated that to Mode S being an improvement on Mode C through the addition of yet other data fields and making the interrogation targeted at a specific aircraft, and Mode ES/ADS-B being a further improvement through automatic broadcasting. In flight school I was taught that Mode C was an improvement on Mode A through the addition of data fields that provide aircraft altitude.

Mode 5 вЂ“ Cryptographically secured version of Mode S and ADS-B GPS position.

Mode 4 вЂ“ 3-pulse reply, delay is based on the encrypted challenge.

Mode 3/A вЂ“ 4-digit octal identification code for the aircraft, assigned by the air traffic controller (the only mode shared with civilian aircraft).

Mode 2 вЂ“ 4-digit octal unit code or tail number.

Mode 1 вЂ“ 2-digit octal 'mission code' that identifies the aircraft type or mission.

According to NATO STANAG 4193 (not publicly available, summary from Wikipedia), the '3' in that description refers to the mode in the Identification of Friend or Foe ('IFF') system: Mode A transponders are sometimes referred to as Mode 3/A transponders.

Ctivo ts mode and skipmode