The DC1 EZ Tone entrance alert is one of our most popular alerts! This mechanical entrance alert is cost effective easy to install and made in the USA. It installs quickly over the existing door frame of the door you want to monitor. When the door is opened the EZ Tone Entrance Alert emits a loud "Ding" sound as the internal metal strip is struck by the metal plunger. This alert is maintenance free requies no batteries or wires and durable enough to last for years to come.