Safe Double Vision Guardian - Ideal Wireless Video Door Phone with Dual Receivers (CMOS Sensor) This product is the ideal video door phone that comes with the latest safety innovations. Differently from most door video phone systems, The product comes with two indoor receivers The advantage of this product is that you could attach 3.5 inch screen receiver on a wall . The Double Vision Guardian is extremely safe and easy to install. The outdoor camera can be simply attached to walls with 4 provided screws.