Mesa 7i33 Encoder Input

Depends on your encoders.
If your encoders are differential (RS-422), they will have 8 wires total (or 6 if they have no index)
and should be run in RS-422 mode. TTL encoders would have just 5 or 4 wires total
In both cases a separate shield wire may be present as well.
I think it would be rare for professionally built machine to use TTL encoders
as they are so much more susceptible to noise than differential encoders.

As far as power goes if the encoders will draw more than a few hundred mA
its best to power the 7I33 from a separate 5V supply and not depend on the flat cable.
If you have a 5I20, the best source is the 5V terminal block on the 5I20

Mesaa 7i33 is a godsend. I am interfacing an RFS Elektronik glass scale made by RFS Elektronik ( part of Haidenhain of late). I had visions of having to build rs-422 receivers but with 7i33 no worries.

I would recomend 7i33T with its screw terminal arrangement in preference to the 50 way ribon cable ( wish i paid more attention to options).