I'm certainly no expert, but I'll give you my basic understanding:
1) The electric current has two paths to go from the tail cap/switch to the head from the battery. The threads are not anodized on the body or the head - this is one path. When the switch is switched on, the current flows through the body and through the threads to the head, and the light turns on at the low level.
When the head is tightened down all the way, the end of the body makes contact with the board in the head. This provides a second path for the current to flow, and when the driver senses this additional current, it switches to turbo mode.
which brings us to the second question, which is closely related to the first:
2) The output of the light is controlled through the driver, which is kind of like a very small computer. The circuitry of the driver is pre-programmed to deliver certain amounts of current to the LED when certain conditions are met.
When the driver is receives current through the threads, and has not received current for over 1.5 seconds, it will deliver "low" level current to the led, and the led comes on at the low level.
The switch, being a "reverse clicky", disengages and cuts off current with a slight press without being fully clicked.
When the current is cut off, and then restored within a time period between 0.0 and 1.5 seconds, the driver switches to the next pre-programmed level. If current is only coming through the threads, the driver will follow the "general mode" programming.
When the driver senses current coming from the threads and the board-contact path, the driver will follow the "turbo mode" programming.
I think. :shrug:
