The 008-120-12 series of alternators were designed for automatic duplex control of motors or other types of loads. They are available in a single phase voltage of 120 VAC. When power is applied to the alternator, the DPDT output relay contacts change state each time the control voltage is disconnected. (The relay contacts are NOT cross wired in this series of alternators.) The "S" Version has the option of a lead/lag/automatic selector switch. selector switch.