This two-way GSM audio device calls you when it detects sounds in its vicinity. Simply insert a GSM SIM card and program it to your desired phone number for call back. This audio device can be used in different locations such as the bedroom, living room, conference room, or office. Insert a SIM card into the audio device and it is ready to use. This two-way audio device offers two key functions: (1) Call the audio device to instantly listen in to conversations. The built-in microphone works within a 7-meter radius. (2) The audio device can call you when it detects sound, making it more advanced than other similar products. Key Features: - Hidden audio device with auto-dialing option - Tri-band GSM compatibility Product Notes: - When sound is detected, the device will call your phone - The device can be recharged using a USB charging cable - This product is intended for professional use and compliance with applicable laws is the sole responsibility of the user. Users must ensure that the product is legal to import and/or use in their country. Specifications: - Primary Function: Tri-band GSM two-way audio device - Materials: Molded plastic - Color: Black - GSM Frequency Compatibility: Tri-band (850MHz, 900MHz, 1800MHz, 1900MHz) - Microphone Range: 5–7 meter radius - Power: Built-in 400 mAh rechargeable Li-ion battery - Voice activation enabled with continuous operation time of 5–8 days - Standby time with positioning function only: 16–21 days - Dimensions: 4.3 x 3.2 x 1.4 cm Package Includes: - 1 x Audio device - 1 x Charging cable - 1 x User instructions