Does a wifi client transmit when not associated?

[mp3car]

Does a wifi client (such as a laptop or phone) transmit anything prior to associating (or attempting to associate) with an AP? I suspect no, but I have searched the web and skimmed various specs and standards and I have not been able to find the answer. If you answer my question, please provide a link to a reference, if you can... Thanks!

[fleem]

An 802.11 client can broadcast a "Probe Request Frame" to find out what APs are nearby. Just google "Probe Request Frame". Its up to the NIC driver how often it sends that, if at all.