Hi,
I went through the star-up procedure again, checked the low RPM warning switch, and it was in the AUDIO position all the time. I flicked it on and off before starting the engine and nothing happened.
Then just before running the engine up I switched it off, and after reaching around 6000 it returned to AUDIO (as HuggyBear mentioned). I then switched it back to the OFF position and reduced the throttle until the RPM limit light turned on, and flicked it back to AUDIO. Still no sound from the alarm.
As a last test I increased the RPM back to operating range and flicked the switch on and off again, but no luck...:(