What is considered Digital or not?

[Geof]

Originally Posted by JerryFlyGuy So infact they aren't absolute but rather..'Close position encoders' Jerry

Every encoder is a 'close position encoder' just some are closerer than others.

[Al_The_Man]

There are basically two types of 'absolute' encoders being used, common one has a track for every bit value, usually starts at 10bits & up, commonly used on robots, the other retains the information by battery backup.
There was in fact a post today in the Fanuc forum, where someone lost the battery on his absolute encoders (battery backed up quadrature) . These have to be re-referenced when first initiallized, after that the machine does not have to be referenced on power up.
The 10~16 bit coded type do not require battery backup.
The Non-battery quadrature encoder has to be first referenced in the controller and then the absolute position is known as long as it is kept powered.
Al.