JRC JMA-3400 Series Instruction Manual page 88

Chapter 2 THE BASIC OPERATION
No. Name
TX/PRF button
USB/Chart Card
40
Description
stops responding, turn off the unit by press the STBY + TX/PRF
button.
Press: Start transmitting (in standby state).
Tune the repetition frequency (when transmitting).
Long press: Turn off the heading line.
USB: Insert USB to save files and update software.
Chart Card: Insert SD card to display map (new pec/Navionics+).