After activating PIR sensor, your MP3 files will be restored automatically (Note: Usually they can be recognized on Win7/XP computers, but not on Win8/10 computers.); Widely used in stores: If you find anyone in Kcrper who wants to pass, you will be warmly welcomed. You can download different audio files according to the application to get the appropriate effect. br />Convenient anti-theft function: when you leave the charge, the sound enters ringtone mode. The record player can attract and remind people who want to chase and deter thieves. Two MM power ranges: equipped with; 3 slots for AAA batteries and USB ports, can be powered by 3 AAA batteries (not included) or the included USB port. (Note: do not use USB instead of audio) The effective range of the infrared doorbell is 4 meters, and the ready sound will be restored. when someone enters the effective detection area. Audio files can be replaced by themselves. Simply connect them to; your computer via USB cable and copy new audio files (MP3 format only). Unique design: Supports memory function. When you select the audio and adjust the volume, the off memory function can activate the off function after entering in power saving mode.