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Ai-otmd the Sections
of members or local interest warrant these.
Suggestions on this subject would be welcome.
The promised informal evening has been fixed
for April 3rd, and whilst final details have yet to
be fixed, it is hoped that this will compensate a
little for the "strictly business" of the war years.
We should like to extend a warm welcome to
new members or any who have been temporarily
estranged. Committee members—you can tell
them by the label—will be pleased to introduce
you.
F. HUNT,
Section Editor.
BIRMINGHAM (South Midland Section)
For the opening meeting" of the Session Mr.
S. A. Hunter, A.C.T.C., the new Chairman of
the Section, chose a topical and interesting subject
and a large audience attended to hear his address
on "Electronic Speed Control of Motors."
Mr. Hunter showed, in a straight and well planned
paper, that although the alternating current
system generally necessitates the use of a constant
speed motor, by the application of certain electronic devices, a variable speed drive can be
obtained.
An unusual paper has also been read by Mr. G.
A. Montgomerie entitled "Mechanical Aids to
Calculation." The paper was interesting and
well prepared and indicated the author's con-
siderable knowledge of the principles and practice
of his subject. The treatment of the various
sections was thorough and the author must be
congratulated for the well prepared photographs
and diagrams which amplified the various points
admirably. It was a pity that the discussion
which followed was such poor reward for the
author's endeavours.
Try It Yourself
Again the appeal is made to all members to
consider writing a paper. The Committee will be
pleased to give you every assistance possible, so
do not let doubt and difficulty be a handicap.
Write a letter now to the Secretary, giving him
your ideas and suggestions; you will be surprised
to find that writing a paper is not quite so difficult.
Perhaps you did not go to our Victory Ball,
and heard all too late that you missed an excellent
Dance. Now we are going to tell you that there
will be another one at the same place, the
Botanical Gardens, Edgbaston, on Saturday,
January 26th, and we know that the demand for
tickets is sure to be heavy—you have been warned.
During the coming year we look forward to
your full support, and the Committee take this
opportunity of sending you Hearty Christmas
Greetings and Best Wishes for the New Year.
ROBERT H. STEWART
Section Editor
ERRATA
In the article on Electrical Computing in the
September issue the author's initials should read
R.B. and not R.M.
On p. 2, col. 2, line 26 read » , U for i«. "M
On p. 6, col. 2, line 4 read p. 147 for p. 1935.
BOOK REVIEW
Wave Form Analysis. By R. G. Manley, B.Sc.
(Chapman & Hall. 21s. Pp.275.)
Any student of the relationship between theory
and practice will find much that is satisfying in
this volume. The book is written against a background of aircraft engine testing, but is applicable.
to a much wider field of interest. The physical
significance of the mathematical processes employed is well brought out, and the general treatment is interspersed with useful details concerning
measuring techniques.
An envelope method of analysis is described,
by which a formal analysis can be made of waveforms containing three or four components. The
method makes explicit several concepts which
heighten the powers of observation which can be
brought to bear during the cursory examination
of a trace. The method does not in all cases
demand that the waveform should be strictly
periodic, but on the other hand it does not provide
a means for making a Statistical estimate of the
magnitude and phase of random components.
Such a technique would be very useful in some
work—for example, in elucidating operator
response in manually controlled follow-up systems.
- A useful survey is given of mechanical methods
of analysis (an omission being the use of resonant
systems'); and of methods of recording wave forms
(an omission being the use of electrically punctured
paper).
A superposition method of analysis is dealt with
at some length, for extracting all harmonics up
to the twelfth. The physical significance of all
the operations remains explicit throughout, which
is a great asset in maintaining interest and minimizing mistakes. The treatment of Fourier series
is happily adjusted to the engineering mentality.
A similar treatment of the Fourier Transform
would be well received.
D. G. O. M.
— 28 —
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