This device uses 2 AA alkaline batteries to power a 1 watt LED. It has 4 power levels, plus on/off, and can run either side up.
The jar light is entirely sealed with no external switches. An internal mercury switch controls all of the modes of operation. It will work under water.
All components are mounted directly to the circuit board (mouse over image above). A small piece of 1/4 inch board is glued to the inside of the lid. The circuit board is fastened to this with 2 small wood screws. Nothing penetrates the lid.
Operation is as follows:
Insert batteries and screw lid onto jar.
Turn over and back quickly to turn on/off.
Turning over while off, turns on, and may be run in this position, or turned back to run in the normal position.
Turning over while on, turns off, and if held in this position for about 2 seconds, cycles through the 4 power levels. Once the desired level is seen, turn over immediately to lock in that setting.
These are really great in a power outage. Even the lowest power level lets you negotiate a room without tripping over your pets.