I beelive one of Vonada's laws is 'There is
no such thing as
ground'.
Well...in a sense. It's a reasonable approximation when dealnig with
low voltages, such as generally occur in computers.
But there _is_ a measurable-in-isolation ground potential in the sense
of "not charged"; if you're working with electrostatics, which usually
means (from computer points of view) very high voltages and very low
currents, this can matter in a practical sense.
To get mildly on-topic, I believe there's a TTL IC
on one of the
boards in an RK05 that is powered between a +10V line (generated o
nthat board) and the main +15V line.
Here's another case where "there is no such thing as ground" can fail:
what you outline works only if there are other loads on the on-board
+10V line that collectively draw more current than the TTL in question
does. (Loading internal to the circuit generating it counts.)
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