This two-way GSM audio device alerts you when it detects sounds in the surrounding environment. To use, simply insert a GSM SIM card and program the device to call back to your phone number. You can place multiple devices in various locations such as bedrooms, living rooms, conference rooms, or offices. Insert a SIM card into the device and it becomes operational. The device offers two main functions: (1) Make a call to the device and listen in real time. The built-in microphone has a range of up to 7 meters, allowing clear audio pickup within its radius. (2) The device automatically calls you when sound is detected, providing remote monitoring capability. This feature enhances its functionality compared to standard GSM audio devices. Key features: Audio monitoring tool, auto-dialing function, quad-band GSM compatibility Product notes: - Triggers an alert call to your phone upon sound detection - Rechargeable via USB charging cable - Intended for legal investigative use by law enforcement or licensed professionals Specifications: - Primary Function: Quad-band GSM two-way audio device - Material: Plastic - Color: As shown in image - GSM Frequency Compatibility: 850MHz, 900MHz, 1800MHz, 1900MHz - Microphone Range: 57 meter radius - Power: Built-in 400 mAh rechargeable battery - Continuous working time: 58 hours (with active monitoring) - Standby time: 1621 hours - 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 settings may cause slight color variations between the image and the actual item. Measurement tolerance: 13 cm.