[elihu]

I'm pretty sure that's not true for 2.4 ghz part 15 devices in the U.S. (i.e. 802.11 wireless).

(I had thought that ISM referred specifically to the 2.4 ghz band, but I guess there is actually more than one band. I do find it funny that that one of the most heavily used spectrum bands is the one where we put all the unintentional radiators like microwave ovens and industrial and medical devices, and then the FCC decided that we might as well let people do unlicensed transmission on that "junk band" because it wouldn't be interfering with anything "important". It's sort of the policy equivalent of the common phenomenon where over time the most important services eventually often end up running on the oldest, slowest computer.)

https://en.wikipedia.org/wiki/ISM_radio_band