Wireless tools: signal strength?

[Martin Schiotz]

Hi,

I'm using wireless tools v.25 on my Linux laptop with a wireless Orinoco pcmcia card. I use the commands iwlist or iwspy to get the signal strength from all access points in range. 

My question is, if the signal strengths I get from these commands are calculated from beacon frames which is send out by all access points all the time as part of 802.11. Which means that no packages are send from my laptop to obtain the signal strengths?

Best regards,
Martin Schiotz