I just received a used 1200x1200 machine controlled via ncstudio. It doesn't have a touch probe but pin 1 on the NCstudio cable is where one gets connected on mine. If you don't have a "mobile calibrator" or a touch plate/probe then you CAN'T calibrate the z axis as it reads this input to tell if the tool has touched the probe.
On my mach 3 machines I have a small piece of 1.6mm thick printed circuit board connected to the touch probe input on the breakout boards and it works perfectly every time.
If I open the IO state tab in NC studio I see a J1-1 indicator. Check your breakout board inside the machine and see if pin 1 is connected to anything. My BOB has pin 1 as the first connector but I've seen pics of other boards where the screw terminals weren't in 1-15 order so double check with a multimeter.
Theoretically if you ground the pin 1 input you should see the state of the IO indicator change on the ncstudio IO state tab.
So, it should be as simple as running a long wire from pin 1 soldered to your "touch probe" pcb. BUT make sure everythign is grounded first and that you can see J1 change if you touch the probe to the tip of the tool. Then measure the thickness of the pcb accurately and enter that as the "touch probe" thickness.
BUT... my machine has 110 volts between the chassis and the PC ground so I'll need to fix that first. Ideally the touch probe would be optoisolated from the PC (on the mach3 boards this is usually done for you).
Once I get the machine positioned where I can access the BOB (at the moment it's wedged against a wall while I clear some space for the machine) I'll do some more testing.