Mercury use (WAS RE: hospital surplus)

[der Mouse]

> There was a trick where you could use two DPDT switches to turn on
> the filament and then HV supplies where no matter which switch was
> flipped, the filaments always came on first.

You don't need DPDT, just DPST.  Wire one pole from each in parallel,
the other pole in series.  The parallel-wired ones control the
filament, the series-wired ones the HV.  In ASCII graphics:

        \                         \
         \                         \
______^  :\_____________________^  :\________  <-- HV switch
         :                         :
        \:                        \:
         \                         \
______^   \_____             ___^   \________  <-- filament switch
   |           |             |           |
   |           |____________ | __________|
   |_________________________|

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