This two-way GSM audio device alerts you when it detects sounds in its vicinity. Simply insert a GSM SIM card and program it to your desired phone number for callback. You can place multiple devices in various locations such as the bedroom, living room, conference room, or office. Insert a SIM card and the device is ready to use.The two-way audio device offers two key functions: (1) Call the device to listen in on surrounding conversations. The built-in microphone captures sound within a 5-7 meter radius. (2) The device automatically calls you when it detects sound, providing real-time alerts.Key features: Hidden audio device, auto-dialing option, tri-band GSM compatibility.Product Notes: - Alerts your phone when sound is detected - Rechargeable via USB charging cable - This product is designed for legal surveillance use by law enforcement or licensed professionals Specifications: - Primary Function: Tri-band GSM Two-Way Audio Device - Materials: Plastic - Color: As shown - GSM Frequency Compatibility: 850MHz, 900MHz, 1800MHz, 1900MHz (Tri-band) - Microphone Range: 5-7 meter radius - Power: Built-in 400 mAh rechargeable Li-ion battery - Continuous working time: 5-8 days with voice monitoring enabled - Standby time: 16-21 days with positioning function only - Dimensions: 4.3 x 3.2 x 1.4 cm Package Contents: 1 x Audio Device 1 x Charging Cable Note: Light reflection and display differences may cause slight color variations between the image and the actual item. Measurement may vary by +/- 1-3 cm.