Control Box PSG 202 - Uses a standard 9 volt battery (not included) for the power source. The internal circuit design makes it extremely difficult for the box to produce a dangerous current. Includes a quick-disable button for each channel, as well as a master on/off switch. Features two channels, each with its own intensity control. There is a master pulse rate control and frequency control (15hz to 200hz). Can be operated with the FEC AC Adapter. Do not use any other AC adaptor with this unit! Please shop carefully. We do not accept satisfaction returns on this item.