The labourTENs machine (which is actually its brand name) has a handy little controller buzzer type button. You had a low level of "buzzing"/stimulation when you are not contracting, and then you press the button when you start a contraction and it puts on a high level of stimulation and then you press the button again when you stop the contraction and you go back to the low level of stimulation. If that makes sense... Pretty easy to use and comes with a good instruction manual. I just whacked the things on my back, kinda where the picture showed them. For DS2, I put it on myself as DH was still asleep (and I didn't want to wake him up). So it still worked, even without proper placement (though I'm sure proper placement would have been better).