Security alarm/device question

Ok so im wondering if anyone knows what security devices walmart uses. not the lil bar magnetic devices, but the ones that are over some of the electronics, its a black circular device with a small red light on it and a speaker, it has 2 long wires that wrap around the item and connects back to the black circular object. If any1 knows what these are called id greatly appreciate it, and no im not trying to steal anything, i was supoose to do a report on security devices and anti-shoplifting techniques and i was wanting to use this device in my report.

thank you