Made by Renschler  in Germany, the Solario  is an entirely solar powered audio variometer. It contains a supercapacitor that allows it to charge in direct sunlight, and continue to operate even under zero light conditions for 45 minutes, longer if there is any light available.
It has an adjustable volume and variable sink alarm to allow you to tune it to your liking. To do so you would use a small screw driver to adjust a 16-position dial through a hole on the bottom of the unit. You can set the volume to 4 different settings from very quiet (e.g. you could put it right next to your ear and not lose your hearing), to plenty-loud. Though I can't tell much of a difference between some of the middle settings, so I'd say you really get 3 volumes. Sink tone is a constant/dropping low note (booooooooop), and can be set to go off immediately (annoying, but fun to test!), 1m/s, 3m/s, or 3.5m/s. Rising tone is a broken and rising pitch/frequency "beeeep beeep beepbeepbeep" that's common to most varios. You can also adjust the sensitivity/lag with an even smaller screwdriver (e.g. jewelers/watch/eyeglass screwdriver), however I've never found the need to do this.
This was the very first vario I'd ever used (strapped to me by my instructor during training just in case conditions were good), and my first soaring flight was 90 minutes long! It was mostly ridge, with a few lively thermal pockets. I now own one of these (black body, not orange), and I think it's ideal as a minimalist or backup vario. Never any batteries to worry about. Pleasing sound, and easy to turn off in flight (only one button).
Solario Manual 
Review by User:Gerg.