Transponders
Join Date: Oct 1999
Location: Melbourne - Australia
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I suspect for the reason that anything digital seems to be in powers of 2. 8 bits to a byte, etc.
Aha, edited to include a link I found. Scroll halfway down the page..
http://www.airpark.org.il/articles/a.../transpon.html
[This message has been edited by Lurk R (edited 22 May 2001).]
Aha, edited to include a link I found. Scroll halfway down the page..
http://www.airpark.org.il/articles/a.../transpon.html
[This message has been edited by Lurk R (edited 22 May 2001).]
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Yeap,
The decimal (octal actually) digits are converted to binary, and the digital string is sent back to the radar site.
0 - 000
1 - 001
2 - 010
3 - 011
4 - 100
5 - 101
6 - 110
7 - 111
i.e. code 7700 is 111111000000, 7500 is 111101000000.
A discussion on mode s transponders just finished, a few external references are in there if you would like further info.
The decimal (octal actually) digits are converted to binary, and the digital string is sent back to the radar site.
0 - 000
1 - 001
2 - 010
3 - 011
4 - 100
5 - 101
6 - 110
7 - 111
i.e. code 7700 is 111111000000, 7500 is 111101000000.
A discussion on mode s transponders just finished, a few external references are in there if you would like further info.
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TA/RA refers to Traffic Advisory & Resolution Advisory.
These are displayed if the aircraft has Traffic Collision Avoidance System (TCAS) fitted and another aircraft is predicted to come close.
------------------
PPRuNe Radar
ATC Forum Moderator
[email protected]
These are displayed if the aircraft has Traffic Collision Avoidance System (TCAS) fitted and another aircraft is predicted to come close.
------------------
PPRuNe Radar
ATC Forum Moderator
[email protected]
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To round this off with a condensed history lesson -
In the dark ages, not long after the first abacus was wired to the mains, the early computer chips used 8 bits, (0-7) to store digital info. This gives, as already stated, 4096 code options. Computers have moved on a bit to 32 bits, giving (aah! can't do it!) a lot more options. 64 bit processors (and 128) are around . Transponders have not yet moved. They will.
In the dark ages, not long after the first abacus was wired to the mains, the early computer chips used 8 bits, (0-7) to store digital info. This gives, as already stated, 4096 code options. Computers have moved on a bit to 32 bits, giving (aah! can't do it!) a lot more options. 64 bit processors (and 128) are around . Transponders have not yet moved. They will.
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BOAC,
just to be picky and fit in with the rest of the crowd...
Eight bits give you 2^8=256 combinations. Mode C uses 12 bits (3 bits gives 2^3=8 combinations, thus 0-7, times four digits = 12 bits) giving 2^12=4096 combinations. Mode S uses 64 bits IIRC, giving 2^64=18446744073709551616 possible combinations. When we reach that number of A/C flying with mode S we will have to think of something else! 
Cheers,
/ft, former computer geek who decided that Al, Ti and Jet-A was more fun than Si
just to be picky and fit in with the rest of the crowd...
Eight bits give you 2^8=256 combinations. Mode C uses 12 bits (3 bits gives 2^3=8 combinations, thus 0-7, times four digits = 12 bits) giving 2^12=4096 combinations. Mode S uses 64 bits IIRC, giving 2^64=18446744073709551616 possible combinations. When we reach that number of A/C flying with mode S we will have to think of something else! Cheers,
/ft, former computer geek who decided that Al, Ti and Jet-A was more fun than Si
