Submarine Hull Is "Mike" - AmericanRadioHistory.Com

522 RADIO -CRAFT March1 1932
PERMEABILITY
RECORDI \G
A new method of recording sound on wire by varying
the permeability of the wire in phase with the sound
to be recorded.
By PHILLIP BERNSTEIN
BEFORE beginning our discourse per -
taining to a new means of sound -
recording, let us briefly review sonic
phases and details of the present and
near -past arts of sound- recording, broadcasting
and reproduction.
Since that great inventor, Thomas A.
Edison, first commercialized his phonograph,
the methods of recording and reproducing
sound have changed very little, with the
exception of sound -on-filin.
Of course, we
now have the use of vacuum -tube amplifiers,
high -quality microphones and pickups, and
fine loud- speakers. However, the same bulky
composition discs are used to a large extent
with either the hill- and -dale, or the duolateral
cut.
The Edison records make use of the hill -
and -dale cut, which utilizes a constant- spiral,
or a constant -screw track which varies in
depth according to the sound impressions.
The pickup or mechanical reproducer is
then constantly varied in a vertical motion
as the needle point moves up and clown
within the sound track. The duo-lateral
cut, on the other hand, has a sound track
of constant depth but which varies from
side to side, according to the sound impression.
In the latter method, the pickup or re-
BOTH HEATING AND
RECORDING CHAMBERS.
FILLED WITH INERT GAS
AT ATMOSPHERIC
PRESSURE.
o
RECORDING
ELECTRODES OF
IRIDIUM OR
TUNGSTEN
ëu: 3r+.nr=`-`sxziZ3' szu
Moo
e
?ILslti.9`,Sc:i`iF..:`iy
t
4 HEATING
CHAMBER
f
producer moves back and forth in a horizontal
position. This method is the most
widely used, both in ordinary records and
in tal'ing movies.
The Telegraphone
Some t' about the year 1900, V. Poulsen
invented his famous telegraphone. It
seems strange that an invention of this
sort, although widely discussed at the time
its patent was granted, should be so quickly
forgotten. In fact, it has been rediscovered
and reinvented a dozen times since.
The telegraphone is a method of recording
sound on wire, disc, or tube by magnetic
means. In brief, a steel wire, No. 28
B & S gauge, passes between the pole pieces
of a magnet which is energized by a solenoid
which, in turn, is energized by a micro-
f
phone or an amplifier. The steel wire then
retains a magnetic record which is reproduced
when the wire is passed again through
the pole pieces, this time with a pair of
head -phones or an amplifier and loudspeaker
attached to the solenoid.
'l'he objectionable feature of this system
of recording is that the magnetic impressions
begin to expand, especially the higher
frequencies. In a day or two, the record
is almost indistinguishable except for the
-INERT GAS"TANK TO
REPLENISH SUPPLY OF GAS.
A SLIGHT AMOUNT OF
WHICH IS LOST THROUGH
COOLING.
RECORDING
CHAMBER
COOLING CHAMBER
FILLED WITH
POWDERED LIME
PYROMETER NEAT INDICATING
INSTRUMENT CONSISTS
bt LIQUID CHAMBER TO O CONNECTEO TODALE
PREVENT ESCAPE
GALVANOMETER
OF INERT GAS.
Fig. 1
Schematic circuit showing the patk of the wire during the process of recording. The two rollers
heat the retire above its critical temperature before the actual recording begins.
The amplifier used by the author during the
recording process.
lower frequencies, the higher ones having
entirely disappeared.
Some earnest investigators have tried to
improve upon the Poulsen telegrapkone, but
the consensus of opinion seems to be that
its fundamental and original faults cannot
be overcome. The magnetic record simply
will not stay permanent.
From London and Berlin, in 1929, we received
reports that the Ludwig Blattner
Picture Corp., Ltd., of London, and the
Telegraphie Patent Syndikat of Berlin, associated
companies, had succeeded in demonstrating
talking emotion- pictures with the
sound record reproduced from magnetic
wire. No reports have been received since
then, although, at the time, it was claimed
a more permanent magnetic record was
produced.
What the industry needs at present is
a record that will run one hour, two hours,
or a whole day, without interruption!
A full hour's program for the home, be
it sound or television or both, is one of the
possibilities that may he secured by reoording
wire.
The author, for many years, has given
Ihonght to such a system and has realized
the faults of l'oulsen's method. A new
theory along those lines was then developed.
Variable Permeability Recording
In a nutshell, what we propose to do is
to vary the permeability or "magnetic resistance"
of a steel wire, and this will he
done with heat.
Annealing is a heating and cooling operation
of a material in the solid state. Among
the purposes are the following: (a) remove
gasses; (h) remove stresses; (c) induce
softness; (d) alter ductility, toughness, and
electrical, magnetic or other properties; (e)
refine time crystalline structure.
Head item (d) of the ahoye paragraph
and you will understand what we propose
to do; but not exactly by annealing as
ordinarily practiced.
(Continued on page 553)