The infrared doorbell has 4 meters 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 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, but 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 welcome, 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 store, switch the sound to alarm sound mode, the Recording Player can induct and alert the people want to approach to the store, scare away 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 Format: MP3 (Bit Rate: 8 ~ 320Kbps), excellent sound quality, 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 egree Angle) Sample Rate: 14KHz<b