1. Make a call to the audio device and you can instantly listen in to conversations! The built-in microphone works up to a 7 meter radius, so set this bug up wherever you want! 2. Allows the audio device to call you when it hears people talking! This feature makes it much more advanced than other GSM audio bugs on the market today. 3. When it detects sound, the bug will call your cell phone 4. You can recharge the audio device by connecting the USB charger cable to the power charger This two way GSM audio device calls you when it detects sounds around its vicinity. How awesome is that? Simply insert a GSM SIM card and program it to your desired phone number for call back and now you're in the business! Trying to find out the truth about what's being said behind your back? Now you can from a distance. You can even place several of these audio devices and set them up at your desired locations like the bedroom, living room, conference room or office. Just insert a SIM card into the audio device and your bug is active and ready for action! Hot spots: Audio Gadget Auto Dialing option Tri-Band GSM Audio Device Primary Function:Tri-band GSM Two-Way Audio Device GSM Frequency Compatibility:Tri-band (850MHz,900MHz, 1800MHz, 1900MHz) Microphone Range:5-7 meter radius Power:Built In 400 mAh Rechargeable Li-ion Battery Turn on the voice control function and the expected continuous working time is 5-8 days Only the positioning function is expected to last for 16-21 days Colour:Black Material:Plastic Size:4.3x3.2x1.4(cm) Package Contents: 2 * Voice Monitor Locator