When you can get it
When you can get it to work, it’s life changing. Unfortunately, it is designed in such a way that every time you use it, you will need to get out the instruction book to remember how to operate it.
It has one button and does a chirping sound. With that single control and response, you’re supposed to be able to turn it on and off and change modes and intensity. How many chirps til you’ve gone to mode 2? Did you miss a chirp? It’s really quiet.
I have no idea why it doesn’t just have a switch to turn it on and another button for mode and another button for intensity. But if you’re able, mid-migraine, to successfully hack the expensive medical device, it does really help.