The infrared doorbell has 4 of effective sensing distance, and it will play the prepared sound when someone enters the effective sensing range. The audio files can be replaced by yourself, just connect it to computer by USB data cable, then copy new audio files(MP3 formats only) to the player. Your MP3 files will playback automatically after the PIR sensor has been activated.(Note: it can be recognized on Win7/XP computer, it may be not recognized on Win 8/10 computer) Widely Use in Shop: When detecting the human body passing, it will give out warm , Greeting prompt, warnings prompt, playing voice advertisement or others. According to the different applications, different audio files can be downloaded to have suitable effect. Two Power Supply Ways: Equipped with 3 *AAA battery slots and Mini USB port, it can powered by 3 * AAA Batteries (not included) or the included Mini USB charge port. (Note: Do not support replace audio through Mini USB). Practical Anti-theft Function: When leave the , switch the sound to alarm sound mode, the Recording Player can induct and alert the people to approach to the , scare thieves. Unique Design: Support memory function, when select audio and adjust volume, after the device enters the sleep status, it can realize the power-off memory function. Specifications: Model: Microsound V22.12 Product Type: MP3 Infrared Doorbell Audio : MP3 (Bit Rate: 8 ~ 320Kbps), sound , two levels volume for option: small or maximum. Built-in Speaker: 8ohm 1W Speaker Sensor: Infrared Induction, support automatic induction Power Supply Mode: DC3V ~ 5V Stabilized Voltage Supply Working Current: 100uA (Sleep Standby Mode); 130mA (DC 4.7V) (Playing Mode) Infrared Induction Distance: 4meters (45d ) Sample Rate: 14KHz Memory Size:Built-in 4Mbit SPI FLASH memory Installation:Ceiling mounted or Power supply: External USB power supply DC 5V or 3 AAA dry batteries (Not Included) Working Current: Sleep Status 100uA; Playing status 60mA Humidity: 10 ~ 85%RH Colour:White Material:ABS Size:90*60*26.6mm Package Contents: 1 * Audio Doorbell Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.