In general, with USB_MSD support for XC Tracer:

If the USB cable is connected to the XC Tracer when the XC Tracer is switched on, the XC Tracer works in USB_MSD mode. Then you have to press the red button for about 1 second to switch the device on or off. In this mode you can copy files to the tracer, download logs to the computer or do a firmware update by adding the new firmware (* .bin file for XC Tracer / XC Tracer Mini & * .iap file for XC Tracer II) Copy drag & drop to the XC Tracer SD card. When the XC Tracer is switched off, the new firmware is then installed.

If the USB cable is not connected to the XC Tracer when the XC Tracer is switched on, the XC Tracer will work in flight mode. Then you have to press the red button for about 3 seconds to switch the device on or off.