The PRO 550 with proven Tri-Tronics technology allows advanced training for the serious professional with easy access to 21 levels of momentary and continuous stimulation tone as well as the ability to quickly switch between 3 dogs. PRO 550 features vibration and tone settings remotely operated beacon lights on the dog device to help locate your dog in low light the ability to add an Upland Beeper (purchased separately) and a built-in BarkLimiter activated on the dog device to help keep the peace at home.