Artesyn Centellis 4100 Installation and Use (2015) - Manual (Page 91)

System Installation
Centellis 4100 Installation and Use (6806800D82E) 93
14.If you want to inform shelf management about the PEM insertion, place the PEM
handle switch to the Closed position. The blue LED starts to blink. This indicates
that the PEM announces its presence to the shelf management controller. Wait until
the blue LED is switched OFF. The switched off blue LED indicates that the PEM is
active.
Even without applying power to the PEM, the IPMC will power up and the blue H/S LED will be
on steady. This is because the system receives power from the other PEM.