The concept of electrical ground began when radio receiver sets were being
manufactured. At that time, many of the components were large and had to be
mounted firmly. Each set was built on a metal chassis. The power transformer,
tube sockets, i.f. transformers and tuning and filter capacitor(s) were riveted
or bolted to it. At that time, a power supply had a power output terminal and a
return terminal. The engineers decided that the chassis could be considered as
a big, fat wire. So they connected the return wire of each of the power supplies
to the chassis. Then every circuit wherever it was located would have a wire
connected to the chassis for the power supply returns. That saved a lot of wire,
made radios easier to build, better looking inside and cheaper. It was a
win, win situation. The circuits return connections became known as chassis
ground. Later the term was shortened to just ground. (Today, we use ground
planes on many of our PCB's. It's the same idea.) So that is where the power
supply ground came from. Now, it seems to be confusing to some if not many
newcomers to the hobby. Some think that every circuit MUST have a ground.
That is not true. This problem is reinforced by our use of ground symbols
on our schematic diagrams. Just imagine if you had to draw a complex
schematic without using ground symbols. Who could see the real circuit with
all those ground wires in place? What a mess that would be! So we take the
short cuts and use grounds. Another confusion seems to come from the use
of the same ground symbol for different power supplies. Not to worry, the
electrons know where they need to go, so they do not get lost. Maybe if
people think of the ground terminal or symbol as just a return to power
supply, the confusion would be eliminated.