Is anyone familiar with electric fuel selector valves as used in automotive applications.  I'm trying to figure out how they operate.  Do they select one line when power is applied to a solenoid type plunger, and then the other line is selected when power isn't applied?  Or does a pulse of power switch them back and forth?  If they maintain the currently selected tank when power is absent, it seems to me that this could remove fuel lines and a leak prone selector valve from a lot of cockpits.  Furthermore, the 6 port models look like they could be plumbed easily to handle return lines.