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I have used one that I got from an outfit in Utah (washach ? something). It has a light sensor and will turn on at dark. Caught some bobcat and had a cougar around one of the traps at night when I used it.
I've used them and caught a couple of cats but if I use bait, lure, urine, flagging, feathers, cage puppet etc. I'm never sure WHAT it was or what sub-combination it was that made the cat commit. I think they are a good idea if you are trapping in an area where you don't know what trails the cats are traveling on or you can't set near the trails. If the cats hear the squeaker they will be tempted to come over and investigate but so could any human busybodies who might distirb or destroy your cage.