Thermionic Valve Cathode Symbols!

[Chris55000]

Hi!

I was reading a couple of old thermionic-valve general theory books a month or two ago in Hay-On-Wye, and both of these had indirectly-heated valve-cathode symbols drawn like a minature tree or bush on top of a vertical line in the lower middle of the valve symbol!

I'm aware that the Continentals used the open (sometimes filled in black) circle a lot in their valve symbols but never a tree or bush!

UK (BS 530/BS 3939) practice is to use a circle only to denote a "cold" or "ionically-heated" cathode only, never a hot one!

(My practice is to draw the indirectly-heated cathode the Wireless World way, as a horizontal line with two 45-degree extensions pointing downwards from each end of the main line, one extending to the envelope with a spot at the junction to denote the pin, the other 45-deg extension stopping short of the envelope).

Has anyone else come across this strange method of depicting valve-electrodes?

Chris Williams

(PS! Scanner not working so having to describe in words!)

[Skywave]

Yes, I have. However, cannot recall when, etc., but I do believe it was on a cct. diag. of Italian origin. Like you, when I first saw that 'symbol', it threw me a wobbler too!

Al,

[newlite4]

Similar to these "shorthand" valve and other component symbols featured in Wireless World March 1947 aiming to be a quick way of drafting circuit diagrams.
Neil

[emeritus]

Christmas tree-like electrodes are used for two of the valves (V1 and V2) in a circuit diagram in the American book "Principles of Aeronautical Radio Engineering" (Sandretto, 1942).

The valve symbol used in Stanley's "Wireless Telegraphy" (1919) may be of interest. Unfortunately I only have Volume 1, and all the other valve circuits are in Volume 2.

[Chris55000]

Hi!

To clarify my first post, I've now attached a paper showing all the permutations of Indirectly-Heated Valve Cathode Symbols I've come across in my lifetime of things electronic !

In my opinion the first two (FIG. 1 - the UK BS530/BS3939 I.H.C) and (FIG 2 - BS530/BS3939 Cold/ionically-heated cathode) are the only ones that belong on this forum and in valve-theory and fault-finding discussions!

I believe another Member made a set of symbols in Adobe Illustrator based on the set found in F.J. Camm's "Beginner's Guide To Radio" but I can't just locate them at the moment!

Chris Williams

[G6Tanuki]

How do you feel about the version shown in http://www.radiomuseum.org/tubes/tube_0z3.html and http://www.radiomuseum.org/tubes/tube_0z4.html ??

[Chris55000]

Hi!

Again, whilst this is a recognised continental cathode symbol, it's not technically correct!

The 0Z4 is a gas-filled ionically-heated device so the open circle as per FIG. 2
in my attached paper is the correct one!

Chris Williams

PS!

The book "International Dictionary Of Graphic Symbols" by Kogan Page has a selection of the most commonly used BS3939 electronic symbols in it's "Electronics" chapter - many central libraries have this book if you can't get BS3939!