1.2.4 inch LED Display: frequency and time are clearly visible; automatic backlight saves energy. 2. Indoor and outdoor use: DC 5V power input mode for home use, and 4 x 1.5V AA battery mode for outdoor use. 3. Knob design for volume: easy to adjust, convenient and practical. 4. Knob design and 2.4 inch LCD display: knob controlled operation paired with a 2.4 inch LCD readout for clear readings. Benefits at a glance: supports reliable indoor power with a 5V DC input and portable outdoor operation via AA batteries; easy volume adjustment through a dedicated knob; energy efficient backlight on the LED display for quick visibility without unnecessary power use; dual display options (LED for critical readouts and LCD for detailed readings) to suit different environments. Use scenario 1: at home or in a small office where a steady 5V power source is available, enabling continuous operation with clear frequency and time readouts. Use scenario 2: outdoor activities such as camping or field work where a battery option is essential, ensuring the device remains functional away from AC power. Use scenario 3: travel or events where easy knob control and a clear display help quickly monitor readings in varying lighting conditions.