The alarm that sounds has nothing to do with calibrating the unit or reversing channels on the transmitter. There's a switch on the MFC unit, referred to in the instruction manual (page 6 - "Adjusting MFC 01 Unit") as "SW2", right above the set-up button (SW1) and the two adjustment pots (VR1 & VR2). This switch allows you to toggle between "Turn Signal 1" and "Turn Signal 2". I'm not sure which is which, but one of them has a really annoying alarm that sounds only when turning right, the other is the traditional blinker sound when turning in either direction. The key when switching between the two turn signal settings is that you need to power the unit down in order for the change to take effect. It took me the better part of yesterday to figure it out. Turns out it's right there in black and white in the manual.
https://www.tamiyausa.com/pdf/manuals/56511ml.pdf
