[Kenny Bunk]

Doug baby, just because it's got a dial, doesn't mean it's an "analog" instrument like Lucky used on the flight to gay Paris.

The input can be strictly digital. The read-out, needle and dial, rather than a screen read-out. Think auto tachometer. The needle and dial you read in a modern car is driven off a sensor, not a spinning cable.

[onedoug]

From Wikipedia's "Glass Cockpit":

Due to the possibility of a blackout, glass cockpit aircraft also have backup analogue displays for key flight instruments such as the airspeed indicator and altimeter.

[onedoug]

I would hope too that the analog instrumentation is fed by separate pitots, which would seem to make sense.