Nest 9 Anti Barking Control Device, Ultrasonic Dog Bark Deterrent, Mini Sonic Anti-bark Repellent 50 FT Range, Sonic Bark Deterrents Silencer Stop Barking Bark Stop RepellerUPGRADED VERSIONUltrasonic anti barking devices automatically detect barking from as far away as 50 feet. The barking control device automatically emits high pitched sounds that only dogs can hear. Once the dog stops barking, the ultrasonic bark control automatically stops emitting ultrasonic sounds SAFE FOR DOGS AND PEOPLEUltrasonic frequencies are harmless to pets and completely inaudible to the human ear, so you can use this device safely HOW TO