PLAN B analog blog

I'm a little confused about the elf leveler module.  The description says it will output a fixed 
voltage when no input is present.  Does this mean--

a) The knob is simply determines how much V is added to the incoming V at any time.

b) There is a switch that detects whether something is plugged into the input socket.  If yes, 
it attenuates any signal.  If no, it outputs a fixed V depending on the knob position.

c) If a nonzero signal is present, it is an attenuator.  If zero V comes in, it outputs a fixed V.

Now, (a) could be of limited use, (b) would be great but seems doubtful, and (c) might make 
for some neat effects but would generally not serve the purposes of audio and CV 
processing.

Or is the answer: (d) The description is a typo; it is just an attenuator?


Thanks,
Monroe