Very simple really:
RX will flash green, press and hold the SW button on the RX until the light changes to red, release the button.
RX will stay red for a few seconds and then go to solid green, done!
3PK does not have the C1 and C2 modes, only the 4PK has that for the 604 receiver which will not work with the 3PK since it only transmits in C1 mode.
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