Audible door entry systems can range from a basic one way to large complex blocks. The entry phone system gives the owner the advantage to talk to the caller before the entrance door is opened. A call from the external panel will buzz the handset within the property. The occupant will lift the receiver and be able to identify the caller. A button on the handset can be operated to release the external door lock. Video Entry Systems: Video entry systems work on the same principle as audible except the occupier will have visual verification of the caller. A small camera is integrated within the external panel and as the caller leans forward to speak, the occupant will have a full image of the caller on a monitor built into their handset.