This is the Economy version, stereostim box. The unit has individual level controls, Isolation tranmsformers and High power current limiting resistors, to ensure saftey.
The Btstim Econo is a traditional Stereostim unit, featuring the same 10 turn level controls, isolation transformers, and current limiting resistors found in our other units. "Traditional Stereostim" means an external signal generation source is required (computer, mp3 player, smartphone). This unit plays all the same mp3 pattern files as our other units, of which there are thousands available online, with a large number available on our free community website http://www.socialstim.com. The Btstim econo is a good choice for the seasoned estim player who is on a budget.