Operational Instructions: Open the insert buckle of the collar and put the collar round the neck of the pet. Adjust the tightness of the collar. Dont make it too tight for not to hurt the pet. Turn on the transmitter by the switch on right side of it. Install the batteries for the receiver. The LED inside the receiver starts to keep flashing. Press vibration or shock button immediately after batteries are put into the receiver firmly. Then the LED will stop flashing and only light which indicates that the transmitter and the receiver have matched each other successfully. If LED stops flashing on its own without press any button in the transmitter, take out the batteries. Wait for at least 10 Seconds and try step 2 again. Put the cover on the receiver firmly. Attach the receiver to the collar. Collar Description Length:66mm Height:36mm Width:38mm. Weight:56g (module+battery) Collar length adjustable from 20 to 50cm Power:21.5V AAA battery (supplied) Water resistant and shockproof.