The second test follows up on the previous testing but adds the function of the TUNE/RESET, AUTO and BYPASS buttons of the automatic antenna tuner ATU-100.
Because the tuner uses the negative logic to control the the TUNE/RESET, AUTO and BYPASS function all three LEDs light of the slave module when the tuner is turned ON (logic 1).
By pressing the TUNE/RESET, AUTO, BYPASS the button on the muster module the appropriate LED on the slave button is switched OFF (logical 0).
OK1TK HAM Radio 