We have get the same problem with the Rutex drives in the past. As Tom from Rutex said *I will never run a real machine with TTL encoder*
The wiring diagram is also different depending of the pdf file....
The way to solve your problem is to use diffential out encoder or use the line driver converter from their website.
USdigital also sell a line driver converter for ttl encoder for less than Rutex.
Here the link for them:
Hope this help,