ULTRASONIC PEST REPELLER-SET OF 9-NEW BY BELL & HOWELL FOR RATS, MICE, SPIDERS, ANTS AND ROACHES. THE ULTRASONIC PEST REPELLER IS SIMPLE TO USE. IT OPERATES ON ANY STANDARD 120 VOLT WALL OUTLET. SIMPLY PLUG IT IN. THE RED INDICATOR LIGHT ON THE FRONT OF THE UNIT WILL BLINK ON AND OF TO LET YOU KNOW THAT THE UNIT IS WORKING. PLEASE NOTE THAT A SLIGHT "CLICKING" NOISE MAY BE HEARD AS THE INDICATOR LIGHT BLINKS ON AND OFF. THIS IS NORMAL. THIS IS SAFE TO USE AROUND PLANTS AND PETS SUCH AS DOGS, CATS AND FISH. UNITS HAVE LED INDICATOR, AC PLUG, ULTRASONIC SPEAKER INSTRUCTIONS INCLUDED.