The Eckhart DSC's arer actually called "Micro-guide III" see www.nova-astro.com
This is an interface set of electronics which talks to encoders on the Alt/Az ( or RA/Dec) axis of the telescope and communicates to a PC say, running The Sky ( or most of the other planetarium packages) to display the co-ordinates of the scope on a map of the sky. You can either have the telescope drives controlled thru the same package ( GOTO) or select an object, and move the telescope until the "cross-hair" lines up on the screen ( Push-to) Uses serial connection to PC.
The NGCMax is a stand alone "computer" with built in database which can display the scope position and directions to the selected object on the handheld display. It can also be connected to a PC as per above.
Both need some additional hardware to connect the encoders to the axis of the telescope.
Hope this helps