From the MESA website; "The 7I33, 7I33T and 7I33TA are a 4 axis analog servo interfaces intended for operation with MESAs Anything I/O cards in motion control applications. The 7I33 takes the PWM and direction signals from the Anythng I/O card and converts them to +- 10V analog output."
The 7i33 takes the PWM / Dir output and converts it to +- 10V analog output. Therefore your servo amps will need to be able to accept these signals.
You will need EMC2. Check out these sites and links;
EMC Documentation Wiki: HostMot2
EMC Documentation Wiki: Pjm
LinuxCNC.org - EMC2 Documentation - HTML version
This should get you started in the right direction.
Hope this helps,