August 1947 QST
 Table
of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
from
QST, published December 1915 - present (visit ARRL
for info). All copyrights hereby acknowledged.
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 There is something about these proposed 'shorthand' circuit
symbols that reminds me of the IEEE digital logic symbols using the 'distinctive shape' (the traditional format)
versus the newer 'rectangular shape' format (examples shown to the left). The set is quite extensive
when all the different flavors of combinatorial blocks - flip-flops, timers, counters, shift registers,
encoders, decoders, etc. - are included. My personal preference, you might guess, is the original format
with distinctive shapes. Although I do not do a lot of digital work, it is easier for me to follow the
signal flow and mentally perform the logic operations with the distinctive shapes. But I digress. This
article from a 1947 issue of QST magazine introduces shorthand versions of analog schematic symbols.
I only need to go to the basic resistor, inductor, and capacitor symbols to develop a bias against them.
They do not seem to have been adopted widely by the electronics community because I have seen a lot
of schematics over the years and do not recall ever seeing these used. However, it is worth posting
them here for the public to find in case someone out there does discover their use and wonders what
the heck is going on. Maybe you need to cut your teeth on the new symbols to like them ... or be a lot
more open to change than I am ;-)
Shameless sales pitch: I have custom sets of schematic symbols available for
both Visio and
Word.
Shorthand Circuit Symbols
The March, 1947, issue of Britain's Wireless World carries a story entitled "Shorthand Circuit Symbols,"
by A. W. Keen, that presents enough new ideas in representing radio circuits to be of interest to all
who deal with the beasties.
Fig. 1- Simplified symbols for "shorthand" circuit representation.
Although Mr. Keen points out that his "shorthand" method was developed only as a faster technique
for circuit representation and not as a replacement, there is much to recommend it for general use.
You can be the judge.
At; Mr. Keen points out, there are four common components that must be represented in radio circuits:
resistance, inductance, capacity and vacuum tubes. These are the ones, therefore, that should be simplified,
since they occur so frequently. The first three basic circuit elements are simplified by reducing the
present symbols to a bare minimum, as shown in Fig. 1. That this "shorthand" presentation lacks nothing
in flexibility can be seen in Fig. 2, where various special forms of the basic components are represented.
Further, when these symbols are combined, they still suffer nothing in clarity and certainly gain in
simplicity, as is obvious from Fig. 3.
Fig. 2 - Special forms are easily derived from the basic symbols of Fig. 1.
Mr. Keen's symbol for a vacuum tube is quite ingenious. He points out that following the various
grids in multigrid tubes is an unpleasant process prone to error, and that one must count the grids
carefully before deciding what type of tube is being represented. To eliminate all this, he represents
a triode by a triangle, a tetrode by a square, a pentode by a pentagon, and so on, as in Fig. 4. The
side of the polygon representing the cathode is made distinctive by superimposing a small heater (resistance).
The other elements of the tube then follow logically in a clockwise direction around the figure, each
element being represented by a side of the polygon.
Fig. 3 - Combinations of the basic components are a simple matter, and they take
less time to draw than the more conventional representations.
Tubes like triode-pentodes and the like are represented by surrounding the triode with the pentode
and using the common cathode as the common side of the figure.
Fig. 4 - The "shorthand" vacuum-tube symbols are based on the use of polygons whose
sides equal the number of elements in the tube. Combination tubes with common cathodes are easily represented.
Several other interesting points were developed in the "shorthand" system. Because the symbols are
small, the average wiring diagram is opened out and there are not many "crossover" points. To avoid
the "loop" used in QST diagrams, or the dot-no-dot system adopted during the war - which often leads
to confusion and error - the "shorthand" method separates a four-wire junction into two separate junctions,
and hence any normal crossover of lines represents no connection. This makes for very simple construction
and considerably less chance of error. Chassis grounds, the usual common return, are represented by
a small "C" superimposed on the end of the wire, resulting in what looks like a bird's claw, or the
letter "E" (for "earth").
A few sample diagrams are shown in Fig. 5. - B. G.
Fig. 5 - Familiar circuits represented by the "shorthand" method.
Posted March 24, 2016
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