Other links in this article led to a clinic, more claims, and devices. Probably things are going to get murky quickly.
Transcranial stimulation is simple and it includes two electrodes along with device running on a 9-volt battery to pass a stable current of 1-2 microamps constantly to form an electromagnetic field for modulating the neuron activity n the cerebral cortex. This device boasts a cathodal electrode as well as an anodal electrode, of which the latter is positively charged electrode while the former is negatively charged. When the switch is turned on, the current passes to the cathodal electrode via the anodal electrode, forming a circuit. The batter-powered device also has controls for setting the current along with the duration of the brain stimulation.
via Transcranial Direct Current Stimulation TDCS: Is it Effective for Treating Depression | Signs of Depression.