(1) Door sensor with two "self contained" alerting melodies Designed for applications where the door is always kept closed, never left open. The alerting system is a wireless magnetic sensor with transmitter that transmits a wireless signal to a remote receiver over 200' away, that has a full range volume control to adjust the (2) different alerting melodies (A) our exclusive one time "ding dong" and (B) pleasant chirp chirp sound. The Model DA2D wireless magnetic door sensor offers another exclusive feature, a wireless "doorbell". With the addition of a simple to install "optional" standard O/C door bell button available at any local hardware store. Simply attaching this standard O/C door bell to our "NEW" direct plug in cable (included) and plugging this cable into the jack on the entry door sensor, the system is now a two function system (1) daytime customer entry door chime and (2) a wireless "door bell", all for the one low price. The DA2D door chime activates only when the door is opened and does not activated when the door is closed or left open.