APW121215, this power supply is currently widely used. Most of the 19 series models use this power supply. The 4-digit number 1215 behind APW12 means that the power supply's output voltage is 12-15V. This power supply has many versions, including a, b, c, d, e, and f. 

The most commonly applicable APW12 1215d power supply models include S19i, S19XP, S19pro, S19j Pro, S19j Pro+, etc. 

The general situation is as follows:

APW121215 a /b /c versions are interoperable (no voltage feedback).

APW121215 d /e /f versions are interchangeable (with voltage feedback).

APW121215 d /e /f version can be used instead of part a /b /c by upgrading the firmware, but the a /b /c version cannot be used instead of d /e /f.