Here’s my solution (it’s the one from the book):
And here’s the link:
Description: This one is a little trickier than puzzle 34 because the gear bits are at the same level (when they’re at the same level, you can’t test them both with one ball). In this solution, I connected a gear bit to the bit A that’s higher up, and another to bit B that’s lower down. Then something can be set up that’s similar to the solution of puzzle 34.