J.P.
There are different types and settings of collars. There is the spray collar, but I have heard that that can shift and then has no affect. There is the no-bark collar that gives a little jolt when they bark. I used these on my grandmother's little dogs (yorkie and chiuaua mix) after she passed because all they did all day was bark. It worked after about the third time they went on a barking rant. You can set the sensitivity of these as well. We set it very low at first, and the dogs didn't even notice it. Then there is the training collar. With that, it is a collar that has the ability to emit a high frequency noise, or shock. So, you could try it with the noise, and if they didn't respond to that, you could then shock. It wouldn't be an automatic thing, and wouldn't have an affect if you were gone (don't know if neighbors are a concern or not while you are away), but is more of an interactive training tool. The sensitivity can also be programmed with those.