For long I've wanted to add a measuring probe to my Maho to practically remove human related centering errors.
I ended up purchasing a practically new OMP60 (1075€) and an OMI-2 in excellent condition (800€). Getting older TS520, APE, MP7+OMI/OMM would of been nearly as costly and they are legacy products already. There are cheaper alternatives, but I bit the bullet in cost wise.
My machine has E-6952 and here is what I did.
I verified the signals from a Heidenhain TS-511 manual that uses APE-510 / 511 (see attachment).
Connected OMI-2 accordingly and set machine start and probe status to "level" with the dip switches. Error line is connected to input 6 / probe status and is set to N/C.
off, on, on, off, off
off, off, on, off, off
I set the probe as "kabelmesstaster". I tried "Infrarot" also, but I didn't have consistent results in activating and deactivating the probe by M27 and M28. I suppose that by setting the probe to "Infrared on" and "auto off" power functions it could work. The OMP60 also supports MP7 style "spin on, spin off".
It's to be noted that M27 and M28 are not required when initiating a G45 or G46 measuring cycle. The machine does it automatically.
Also, with the setup I have (or because of machine property) when the probe has been activated with M27 and G45 is used to measure in Z (G45 Z0 K-1), the machine throws a collision error outside measuring cycle/M3. This happens only in Z direction (I have inverted axis, btw). If M27 is not used, the cycle performs flawlessly.