A tether device allows a pet to roam freely within a pre-defined area of space while restricting the pet from moving beyond the perimeter of a pre-defined area. The location of the perimeter is programmed into the tether device by providing distance and angular coordinates of the distal end of the tether from the tether device. The location of the pet, once attached to the tether device is likewise determined by the combination of coordinates. When the microcontroller senses the pet is nearing the perimeter of the pre-defined area, a lock mechanism is activated which prevents further movement in a direction that will exceed the perimeter, and only allows movement of the pet away from the perimeter. The lock mechanism may have a cushioning mechanism to prevent a hard stop. The tether device can also generate alarm tones to alert the user and/or train the pet.
