On the back of 4 different miners in the tunnels is a 2-digit number. You've killed 3, so if you haven't already got the numbers you'll need to go back and get them. The guy across the track has a number too, it's with the remaining numbers. The first digit of the numbers are 1,2,3 and 4. Same with 2nd digit. The first digit is which switch to use, the second digit is what to set that switch to
So if the numbers you have are 13,24,32, the final number will have to be 41. And you'll need to set the switches to