ご質問: How do I know the power supply is the single rail type or multi rail type?(3/1/2022) 答え: You can check the label on the power supply, it show the detailed specification of the power supply.
If you only see one "+12V” on your power supply, it means your power supply is "single rail” design.
For example.
If you only see multiple"+12V” on your power supply, it means your power supply is "multi rail” design.