Features: Multifunctional practice device: Supports manual button connection with built-in precise oscillator for professional Morse code training. Double interfaces design: Features a standard 6.5mm (compatibles K4 key 6.5mm connectors). Adjustment sound: Rotary controls for sound adjustment, delivering clear, resonant tones suited to diverse practice environments. Exceptionally Battery Life: Features a built-in battery with USB charging capability. Automatically power off when fully charged, ensuring prolonged operating for practice convenient. Portable and Compact: Measuring just 110x62x28mm, it is easily portable for use at home or outdoors. Specifications: Size: about 110×62×28mm/4.33x2.44x1.1in Interfaces: 6.5mm key socket Power supply: USB charging Battery Accessories: USB charging cable (adapted to mobile phone charging head) Package Includes: 1PC Practice Oscillator 1PC Connection line note: Please allow 1-2cm errors due to manual measurement. Please allow for slight color differences due to different display resolution