how does wifi power reduction work?

[#1]

[Hope this hasn't been asked before- couldn't find anything with the search function]
I mainly use wired connections, wireless only occasionally. If I enable wif power reduction, does anyone know:
1. Do I just have to start up a wireless device within range for the wifi to turn on?
2. How long does it take after closing all wireless devices for the wifi to turn off?

[#2]

Hi there,
That feature is actually disabled on our routers because we noticed that it can be quite problematic.
With regards to other devices we believe that the router polls frequently for devices rather than the wireless being constantly active rather than it being initiated or deactivated by wifi devices being used in the vicinity.
Adam