Transponder question
 

Frome Wikipedia:

"Squawk codes are four-digit octal numbers; the dials on a transponder read from zero to seven inclusive. Thus the lowest possible squawk is 0000 and the highest is 7777. There are 4096 permutations of these four digit codes, which is why they are often called "4096 code transponders."

Wouldn't there be 7777 permutations or possible codes from a transponder. I am assuming that permutation means code.

8 possible codes in position 1 (numbers 0 -7), multiplied by 8 possible codes in position 2, multiplied by 8 possible codes in position 3, multiplied by 8 possible codes in position 4....

equals 8x8x8x8 = 4096 permutations

it's octal not decimal!:=

How do you propose inputing code 7689?

Case closed! :E

000___0
001___1
010___2
011___3
100___4
101___5
110___6
111___7

I don't know if the order is correct, but you have an idea, now, right?

That's 3 dials of binary with a 4th of octal.

4 octal dials would be as per posts 2 & 3.

(I'll forego the usual quip of there being 10 types of people in the world etc etc).

It would seem to me that starting from code 0000, 0001, 0002 etc all the way up to 7777 would give me more that 4096 selection possibilities. What am I missing here?

:ugh:

Uhg! Basic math is the short answer.... but that might be unfair.

Each digit can only be set from 0 to 7 giving 8 options.

There are 8 x 8 x 8 x 8 possible combinations = 4096

If these digits could select 0 to 9 then there would be 10 options per digit, and 4 digits gives 10 x 10 x 10 x 10 = 10000 (the expected answer) i.e 0000 through 9999

"Are we there yet?"

- GY :E

The person asked a simple question about something they did not fully understand. Many of your responses have an undertone, or more, of sarchasm and derision. Let's hope none of you are, or become, trainer/checkers.

Well...Thankyou Punkalouver and to gusting et al.......

I'd actually never stopped to think about this or even ask why..??

But, now I understand something that I had never previously spent a single thought on.
I just 'accepted' how to use, set the numbers, etc.

Thanks Guys....:ok:

Its just a 'little' thing I know....but.....:ok:

This is also known as Base 8.

0000
0001
0002
0003
0004
0005
0006
0007 (here's the tricky part . . .)
0010
0011
0012
etc.

and e.g.

6776
6777 (note the big skip here. . .)
7000
7001
etc.

You're simply skipping numbers with 8 and 9 in any position. Take all of those numbers (e.g. 1008, 7890, 8001. . .) and subtract them from 10,000 and you get . . . 4096.

Exactly

that's the way we would count if we only had four fingers per hand, like Homer Simpson

Oh-oh - I just checked, and found out I only have four fingers on each hand (plus, of course, the thumb). My medical examiner has never commented on this. Could this be a career-limiting medical condition? Could Homer pass a Class 1 medical? :}

Gusty

***Unashamed thread creep***

Over the past few years I have sensed a frustration at the trivial problems posed by a number of posters.

This is Tech Log, not wannabes. It used to pre-suppose a basic knowledge level. Now it seems to be a place where neophytes come to stop them having to read some books and do some sums.

This is the place where I used to come and read the (without blowing smoke up his ass) well respected analysis by such folks as Old Smokey ( and, no matter what I think of his Command style, of some of what 411A has to say).

I am aware that the above may seem a bit "up myself" but as a Ppruner since before the mid-90s server crash, I offer this as historical perspective.

Old Smokey and the "infamous" 411A themselves intervene often in such amateur posts.

And many times I learn something I didn't expect to learn. Gusty only tells us not to be so tough with the newbies, amateurs or wannabes who dare to post in this presigious forum.

And I have a question as a non-native english speaker:
The thumb is not a finger???:}

punkalouver, thank you for your question. I had never thought about the actual number combinations before but your question has resulted in an old fart learning something. Never realised the little black box was a Base 8 unit.

...and some of us remember back to the days of the 2 digit 64 code transponders. I seem to remember that the change came around 1970?

Anyone else?

mcdhu

Oops, now the obvious makes sense. But hey...

They say there is no such thing as a stupid question. Maybe not true. Never did agree with that but still glad I asked.:\

A squawk code is essentially no more than a sequence of 12 binary digits (bits), each of which can have one of 2 values: 0 (off) or 1 (on).

It's purely for convenience that the 12 bits are customarily divided into 4 groups of 3, to make it easier for us humans to remember them. Three bits make one octal digit (because 8 is 2 to the power of 3).

Incidentally, the Americans do the same trick with the ICAO 24-bit aircraft address that's also used in a transponder, splitting them into 8 groups of 3 bits, i.e. 8 octal digits. Most other countries choose to use groups of 4 bits (hexadecimal digits) since that way you end up with a 6-digit code that's easier to remember than an 8-digit one.