## Wednesday, July 25, 2007

### I'm no hardware engineer

And why you would want to do this is beyond me. But here's today's puzzle.

A computer cable has seven connectors, arranged in a perfect circle -- so by rotating the plug, it can be connected to the outlet in any of seven different ways. Each of the connectors is numbered from one to seven, each number being used exactly once. The same is true for the holes in the outlet. The device that uses this cable only requires that one of the connectors match up to its corresponding hole in order to operate. How should you number the connectors on the plug and the holes in the outlet so that, no matter how the cable is rotated and plugged in, at least one connector matches up?

1. Stagger the other connector leads:

Plug Socket
a a
b e
c b
d f
e c
f g
g d

2. or, just number them in reverse directions...

1 7
2 6
3 5
4 4
5 3
6 2
7 1

3. label the male DIN connector forwards
Label the Female DIN connector Backwards:

1,2,3,4,5,6,7
7,6,5,4,3,2,1

4. There are three possibilities that I know of:

Solution #1

Number the connectors clockwise, with consecutive numbers: 1, 2, 3, 4, 5, 6, 7. Number the holes clockwise, with every other number, then wrapping back around: 1, 3, 5, 7, 2, 4, 6.

Solution #2 (as mr don answered)

Number the connectors clockwise, with consecutive numbers: 1, 2, 3, 4, 5, 6, 7. Number the holes clockwise, skipping every other hole. The end result will be: 1, 5, 2, 6, 3, 7, 4.

Solution #3 (as Abe and karnov showed)
Number the connectors clockwise with consecutive numbers: 1, 2, 3, 4, 5, 6, 7. Number the holes counter clockwise with numbers 7, 6, 5, 4, 3, 2, 1.

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