It is a ZProbe we made ourself.
An electromagnet takes out a rod, on this rod is fixed a blade which hides or not a standard optical endstop.
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The 5V regulator on an expansion board is rated at 1A total. The MCU takes about 0.1A.
Note, large servos dump power into the +5V rail when they decelerate. The internal 5V rail on the expansion board (and the Duet 3 main board) are protected against over-voltage, but could damage anything else that you connect to the 5V outputs.