ditto on the counter
The two round holes on the side are the give-a-way.
One is the transmitter, and the other is the receiver.
When someone walks past it they reflect what is being transmitted ( infrared light? ) back to the receiver, which then adds one to it's counter.
I also have seen one on the Half Dome Trail. It was on the John Muir Trail a few hundred yards from the start at the Old Gage Station. As you were heading up hill it was hiding behind a tree just a few yards off trail. It wasn't too obvious, but if you knew what you were looking for you wouldn't have had any trouble finding it as you were walking downhill/trail.
The one I saw didn't really stand out. The one in the picture you have is like a fish-out-of-water. No effort at all to hide it!!
They've put these up to know how many people are going up trail. The ruckus about the Half Dome cables means they need some data/numbers on trail usage.
Edited 1 time(s). Last edit at 11/17/2011 12:24AM by qumqats.