Seven Ferrite Rings For the Laser-Lords in Their Dark Labs of Cinderblock

OK, more than seven. Ferrite rings (aka cores) are used as inductive loads in circuits, among other things. Any alternating current in a wire creates a magnetic field. By looping the wire through the ring a few times, you will create a changing magnetic field inside, which will produce eddy currents. These currents create fields which oppose the induced changes (this is Lenz’s law). From the circuit’s point of view (I hope it will excuse me anthropomorphizing it; I know circuits dislike that) this is an inductive load, so the alternating current sees a higher impedance than the DC, and this knocks down any high-frequency noise you might have and reduces what you write onto the components being powered.