Transcranial Magnetic Stimulation (TMS) is a technique to stimulate brain tissue directly through the skull. It works by sending a very high current pulse through a coil that is located on the subject's scalp. The fast-rising edge of the pulse induces a current in the brain tissue, causing neuron stimulation.
This device uses a capacitor bank, high current SCR, trigger circuit, figure-8 (or butterfly) coil, and high voltage charging circuit.
Link to the SCR datasheet: http://www.5scomponents.com/pdf/5STH_30J4501.pdf
Some good technical information: http://www.abovesobelow.com/TMS/cTMS.pdf