Mode switching: short press the "connect" key (press for no more than three seconds) to switch between the three modes. Bluetooth mode: Press and hold the "connect" key for three seconds in Bluetooth mode to enter the pairing state (red light flashes slowly), you can use your computer or cell phone and other Bluetooth functions to search for the device with the name You can search for the device with the name "MK321-Pro" by using the Bluetooth function such as computer or mobile phone, click on the name and connect in reverse, the red light of the device will be on for 2 seconds after successful connection and then turn off. 2.4G mode: 2.4G mode long press the "connect" key for three seconds to enter the pairing state (green light slowly flashing), then the receiver into the computer, the device and the receiver will Automatic pairing, after successful pairing device green light will be on for 2 seconds and then turn off. USB mode: the device USB mode through the USB cable connected to the computer can be used as a wired foot pedal, you can set the function through the software. Programming software download website: https://pcsensor.com/article1/download-footswitch Specification: Item Type: 3 Keys Keyboard Material: ABS Size: 75x37x28mm Lighting Effect: Color Backlight Connection: USB Wired, Wireless 2.4g, Bluetooth Battery Type: Built in 140mAh Lithium Ion Battery Applicable Equipment: Computer Universal Package List: 1 x Mini 3 Keys Keyboard 1 x Receiver 1 x Data CableWIDE RANGE OF APPLICATIONS: One handed 3 keys macro mechanical keyboard is easy to operate, convenient and easy to carry. Suitable for office, game, music, media, laboratory and other fields, is a good helper for designers and video editors and many other types of users. ERGONOMIC DESIGN: 75x37x28mm size, ergonomically designed keys with curved surface to fit human fingers, easy and comfortable to trigger. With RGB backlight, it can bring more gaming experience to users. FootSwitch SOFTWARE: Download the latest version of FootSwitch software, install and run the software, switch the device to USB mode (blue light on), connect to the computer via USB cable to customize the settings, save it and it will take effect. (Note: Currently the software only supports Windows system.). MULTI-SYSTEM COMPATIBILITY: After the software-defined settings based on Windows, it can be used in Dos, Windows All, Mac, Linux, OS, Android and other systems. INTRODUCTION: This is a Bluetooth + 2.4G + USB tri-mode mini 3 keys keyboard, the keys have the function of customization, through the supporting software to define the keys as keyboard, mouse, string, multimedia and macro definition functions.