To start with I understand that a diode allows for a one way flow of electricity once a minimum amount of voltage is applied.

On my WOZ the diode on the "Winged" target switch broke. I mean literally the lead broke off so I replaced the diode.
When I was doing this I was surprised to see 3 separate tabs on the switch. I am used to only having two tabs on a switch that are connected, not three. In this case there is a tab that is only connected to a wire, a tab that is only connected to the cathode end of the diode and a tab that is connected to both a wire and the anode side of the diode(I'm guessing this is the negative or ground side.) My first question is: How does this switch work? And what is the benefit of this design over the standard two tab switch?

And now I am curious to understand how the diode is used in this instance. I understand how diodes are used on coils to protect the high power transistor but scratching my head on how it is used in this switch. The diode I needed to replace is a 1N4004 (400V 1A.) My local electronics store had their diodes labeled with NTE #'s. The chart said I could use a NTE116 for a 1N4004. However the NTE116 is a 600V rated diode and the 1N4004 is a 400V rated diode. My second question is: Won't the 200V difference (600-400) between the two have an effect on the operation of the switch? Or would any 1A diode work in this case as long as it is rated at or above 400V?

Thanks!