This two-way GSM audio device calls a programmed number when it detects sound in its vicinity. Insert a GSM SIM card and program it with your desired callback number. It can be set up in various locations such as a bedroom, living room, conference room, or office. This device has two functions: Make a call to the device to instantly listen to conversations via its built-in microphone, which has a range of up to 7 meters. The device can be set to call you automatically when it detects voices. Product Microphone Range: 5-7 meter radius Power: Built-in 400 mAh Rechargeable Li-ion Battery Expected continuous working time with voice control: 5-8 days Expected continuous working time with only positioning function: 16-21 days Dimensions: 4.3 x 3.2 x 1.4 cm Package Included: 1 Listener 1 Charging cable 1 Instructions