See & hear your visitors before you open the door Communicate with the visitor via the telephone & unlock the door from the monitor Ideal for people who live on their own the elderly & school children home alone Record who has been to your home when you have been out Equipped with an unlock button so you can unlock the door from the monitor & not answer the door directly 4 inch flat CRT screen for a clear image of your visitor Simple installation When you have a visitor calling round they press the call button on the exterior intercom unit that sounds a bell in the house to alert you. An image of the visitor will automatically be displayed on the interior monitor so you can identify them before opening the door. With a handy mechanism called the unlock button you can unlock the door from the monitor without walking to the door.