It's not digital. This particular case is a common collector configuration.
Read everything here:

http://www.allaboutcircuits.com/vol_3/chpt_4/index.html

2007/2/7, Lindy Mayfield <lindy.mayfield@ssf.sas.com>:
>
> Please, kindly, elaborate. "Between on and off" sounds like a digital
> circuit, and I'm seeing everything in binary.
>
> Lindy
>
>
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