Delta DPS-1200TB 1200W Power Supply Enable Pinout
These power supplies have been around for a while, these two came out of a Pure Storage array at work after a SAS to NVME upgrade project.
The power supplies themselves are dedicated 12V Rails, and have documentation. The challenge was finding the correct datasheet and understanding the pinout.
The Top of the PSU on the left hand side starts out with 7 individual pins, before moving on to two larger sets of merged pins. The first pin is labeled A25 which is quickly referenced in the datasheet above. This means that A29 can be shorted to Ground to Enable the PSU.