What exactly is "powerfail? " Thanks!

Because the empeg-car is not permanently wired to power in the car (in most installations) and people expect to just unplug it at home without performing an orderly shutdown the unit needs a mechanism for saving the current playback position.

When the input voltage drops below around 11 volts a "powerfail interrupt" is raised and the unit has a few milliseconds to save its state before the power completely disappears.

If your battery voltage is low or intermittent, or when the battery voltage dips when starting the car this powerfail interrupt can be called. Once the powerfail is triggered it is automatically disabled. To differentiate between real power failure and dips in the power the empeg-car notices that after two seconds the power still hasn't really gone away (since it is still running) and there haven't been any more interrupts so it reenables things, turns the display back on and returns to normal.

However, if the unit continues to receive power fail interrupts then it cannot reenable them since the display would keep going on and off. In this situation it does the best it can by leaving them disabled and putting an indicator on the screen. If this happens then pulling the power will not save the state of the unit.

HTH

--
Mike Crowe
I may not be speaking on behalf of empeg above :-)