Originally Posted by
mikemey
There should be 1 sign that is standard for every NoS: It should state:
1. What the machine is
2. What it does
3. That it is optional to go through the machine, and what the alternative is.
As a data point, these signs do
technically have the information you mention. Looking around for something else, I stumbled across the following links, which are the signs that I've seen, poorly placed, in the airports that I have transited.
MMW
http://www.tsa.gov/assets/pdf/mmw_info.pdf
Backscatter
http://www.tsa.gov/assets/pdf/mmw_info.pdf
The backscatter one does, indeed mention, in bold, that the scanner is optional. (n.b. I have not personally encountered the backscatter. Hence I have not seen the sign
ORDOfcr describes.)
However, the poor design and placement of these signs makes it so that understanding that point is not a given for the majority of travelers who don't even know what they are stepping into.
Of course, they don't really describe the alternative as we've heard it relayed here and elsewhere. And that is also a problem.
Let me add my thanks to ORDOfcr for his/her professional and reasoned response. We'd get a lot further if everyone adopted this posting style.