We use them they are that good... Unit on the wall at the gate has 2 mounting screws and is battery operated. Unit inside the house plugs into your nearest power socket.. Easiest most reliable Wireless Intercom on the planet. Has a range of 100m and is water resistant. Good batteries last 1 year and then it is a simple job to replace them. This unit won't fire an electric strike, however if this is your aim we have a great way to do this via our remote control. product has a 1 year warranty.