Yes, you will need to have a power over Ethernet injector in order to introduce the power onto the Ethernet cable at the input side.
The Pi PoE Switch will split the power/ethernet at the Pi end. The power will be sent to the Pi over the GPIO pins and the ethernet via a short patch cable as seen in the photos.
The Pi PoE Switch HAT is electrically compatible with the original Raspberry Pi versions, however it will require an extended height stacking header or GPIO cable in order to physically connect.
There are also a limited number of Model B kits available which are self assembly kits designed for the original Raspberry Pi.
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