This trainer has two working modes. It can be used for CW training on computers and mobile phones. It is compatible with various systems and supports plug-and-play operation without requiring drivers. When using the trainer with a mobile phone, an OTG adapter or OTG cable is required. USB interface: Connects directly to a computer or mobile phone via an OTG device. Electric key interface: Connects directly to hand keys and electronic keys. To connect a hand key, attach the hand key first, then connect the mobile phone or computer. The device automatically detects whether a hand key or electronic key is connected. Button: Switches between mode one and mode two. Press and hold the button to switch modes when connecting to a computer or mobile phone. In mode one, this button controls mouse cursor movement—press and hold to move the cursor downward; continue holding at the bottom of the screen to move the cursor upward from the bottom. Indicator light: Shows operational status. A solid light indicates mode one, suitable for mouse-operated training software or apps such as Lakey, CWPlayer, and MorseTrainer. A flashing light indicates mode two, suitable for specific training software or apps such as VBand, MorseMania, and MorseIt. Name: CW Key Trainer Specification: USB interface Color: Green Material: Plastic Package Contents: 1 × CW Key Trainer Note: Color appearance may vary slightly due to lighting conditions and display settings. Measurement tolerance is ±1–3 cm.