Opperating voltage of RS232

Hi,
I'm working on connecting a VFD {powerflex 755} to the alpha and I wondering what the operating voltages is for the RS232 headers.
however, it not that helpful for what I need. 
The powerflex operates at -10 and +10 I believe (https://literature.rockwellautomation.c ... _-en-p.pdf)

1. Am I able to use arduino for the read/write of RS232 GPIO headers? 
and if so what is its operating voltage?

2. If not what portion of the GPIO headers is controlled by the arduino?

3.Is the usb headers controlled by the arduino or cpu?

Thank you