Features: The detector is super sensitive, not reporting false alarms. It can plug in or use battery. Fully automatic infrared sensing, with strong sensitivity, can not be affected by light. So the doorbell can be sensed during day and night. The swivel bracket makes it easier to adjust the monitoring angle. You can place it anywhere or fix it on the wall. The built-in speaker of the host has a welcome loudness of 855 decibels, which is the loudest in the welcome family. 16 music infrared welcomes(available in day and night) has two levels. The first level is welcome, and the second is dingdong & 16 music & alarm sound (adjustable). Powered by 3 AA batteries, it is energy-saving and durable in use. (This unit does not include batteries). Remote detection can reach to 0-6 meters, and the available temperature is 0-25 degrees. Widely suitable for shops, warehouses, office buildings, factories, and homes. Specification: Color: White Material: ABS plastic Sound: The first Level: Welcome The Second Level: Dingdong +16 music + alarm sound (adjustable) Battery: 3 AA batteries (not included) Remote Detection: 0-6 meters Applicable Temperature: 0-25 Installation and Use Method: 1. Push the battery cover on the back of the doorbell in the direction of the arrow, install 3 AA batteries (alkaline batteries are recommended) and cover the battery cover. 2. Turn the doorbell switch to the voice or alarm level. 3. When a guest enters, the welcome doorbell will sound what you have chosen before. Package List: 1 x Welcome Sensor 2 x Base Note: 1.Each time the battery is installed, the product needs to be self-tested for about 15-20S, and then enter the normal working state. 2.Sensitivity and volume have been set in standard state, not adjustable. 3.If the product has an automatic sound or abnormality, please check the battery power supply or the installation position is correct. 4.Avoid directly facing the illuminating light / sunlight / reflection / direct exposure, if the ambient temperature is too high (above 30 degrees), the device will appear from far to near, which is in normal.