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. To use this trainer on 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 automatic keys. To connect a hand key, connect the hand key first, then connect the mobile phone or computer. The device automatically detects whether a hand key or automatic key is attached. Button: Switches between mode one and mode two. Press and hold the button when connecting to a computer or mobile phone to toggle between modes. In mode one, pressing and holding the button moves the cursor downward. Holding the button at the bottom of the mobile screen causes the cursor to move upward from the bottom. Indicator light: Shows the current operating mode. 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 other 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 may vary slightly due to lighting and screen settings. Measurement tolerance is ±1–3 cm.