The ΤΈ-25 operates on 117 volt 60 cycle alternating current. To energize the unit, rotate the METER switch knob clockwise, from "AC OFF" to "OFF". After a short delay, the face of the BALANCE indicator tube will light up with a green glow. Allow approximately 5 minutes for warm-up. MOTE: the indicator tube will be lit only when the METER switch is in the "OFF11 position. Therefore, as you read the operating instructions, always assume that the METER switch is at the OFF position, unless specifically different instructions are given.