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Mode S transponders are compatible with Mode A and Mode C Secondary Surveillance Radar (SSR) systems. [2] This is the type of transponder that is used for TCAS or ACAS II ( Airborne Collision Avoidance System ) functions, and is required to implement the extended squitter broadcast, one means of participating in ADS-B systems.
Secondary surveillance radar (SSR) [1] is a radar system used in air traffic control (ATC), that unlike primary radar systems that measure the bearing and distance of targets using the detected reflections of radio signals, relies on targets equipped with a radar transponder, that reply to each interrogation signal by transmitting encoded data ...
The basic concepts from Mode S were then militarized as Mode 5, which is simply a cryptographically encoded version of the Mode S data. The IFF of World War II and Soviet military systems (1946 to 1991) used coded radar signals (called cross-band interrogation, or CBI) to automatically trigger the aircraft's transponder in an aircraft ...
Primary radar determines range and bearing to a target with reasonably high fidelity, but it cannot determine target elevation (altitude) reliably except at close range. SSR uses an active transponder (beacon) to transmit a response to an interrogation by a secondary radar.
The original design had three such "modes", Mode 1 was triggered by the interrogator by sending the two pulses 3 μs apart (±0.2 μs), Mode 2 was 5 μs and Mode 3 was 8 μs. [ 10 ] The response to these interrogations remained simple; a successful interrogation on Mode 1 or 3 caused a single pulse to be sent in reply, very shortly after the ...
The Gillham interface and code are an outgrowth of the 12-bit IFF Mark X system, which was introduced in the 1950s. The civil transponder interrogation modes A and C were defined in air traffic control (ATC) and secondary surveillance radar (SSR) in 1960.
Mode 3/A is used to identify each aircraft in the radar's coverage area. Mode C is used to request/report an aircraft's altitude. Two other modes, mode 4 and mode S, are not considered part of the ATCRBS system, but they use the same transmit and receive hardware. Mode 4 is used by military aircraft for the Identification Friend or Foe (IFF ...
IFF doesn't have multiple modes. SIF (SSR) has multiple modes. IFF has only one mode (Mode 4). There is a new Mode 5, but this isn't the IFF we are talking about here. Mode 5 is really a crypto Mode S and ADS-B. I would get rid of all the references to SIF (selective identification feature). OK, did that, hope it works for you.