On one of the now defunct Yahoo Minolta groups someone had found or published a document on the pinouts, voltages and signal structure of the Minolta TTL flashes. I may still have a copy somewhere buried in a backup somewhere. If it's on tape however I longer have a tape drive.
As I recall, most likely incorrectly, the voltage was 3 volts DC. One pin was used to signal when to "quench" the flash. The other was the "dedication" pin which would signal when the flash was ready, set the sync shutter speed, and signal by making the LED in the viewfinder flicker for flash exposure confirmation. I remember my Sunpak flash wouldn't flicker the LED even though the ok light on the flash would light. The viewfinder LED would light but not flicker and go out sooner than with Minolta PX flashes. Minor incompatibility.
Edit: Here's this, but it doesn't document the voltage and signal structure. It gives the voltages for the later iISO (Maxxum) flashes but not the earlier TTL.
https://www.mhohner.de/sony-minolta/flashcomp_techref.php