Evening star., 1923-06-10
Bl PAUL GRIGGS.

Radio is branching out from the
field of communication and amuse-
mont into the realm of medical SCI
ence and legal Jurisprudence, Its ap-
plication-or, rather, the application OF
it's recognized present-day nucleus
tho three -electrode thermionic vac
uum tube-appears to be as unlimited
as the effects Of radio in space is un-
limited.
The tube. in conjunction with the
microphone, will simulate the human
vocal powers: IN conjunction with the
telephone, it stimulates the human ear.
IT'S faithful accuracy as speaker"
is equaled only by its delicate sensi-
ttvity as listener
The tubes most recent application
in practical. useful service is in the
"Audiometer." an electrical device
WHICH is likely 70 eventually become
as familiar an object in our hospitals
and law courts as the radiophone re
"eiving set now is in hundreds OF
thousands of our homes.
Device May Help Hearing.
II is not impossible that. in minia
fure form and as only a Strengthener
or reproducer of sound waves. il will
eventually be worn as an aid to hear
ing, in much the same manner that
spectacles are now worn by those af-
hicted with impaired or defective
vision.
The audiometer is an electro sound
producing and sound recording or
measuring device. developed in the
laboratories OF the Western Electric
and American Telephone and Tele-
graph companies.
Although developed for the investi-
cation and study of the properties
and effects of sound waves produced
by human speech, with i view only
10 effecting refinements in our ex-
Iensive networks Of remarkably ef-
FHone systems, its practical applica-
lion TO medical science and Legal
perscns afticted with vary ing degrees
of deafness.
Incidentally, it is the radio OF
vacuum tube. and that alone. that has
made possible our preSent-day trans
continental land wire telephone serv-
ice. as outlined in my article of April
!, 1928.
Method of Operation.
The audiometer consists OF vacuum
tubes associated with a local cleo
trical oScillatory tran smitter'' cir
Cuit. and with a thermal or energy
6issipating receiver circuit, tho lat
ter including the windiugs OF a tele-
phone.
Electrical oscillations of any desir-
ed frequency and of any desired am
nlitude or strength are produced in
the tran smitter circuit. The desired
'requency is obtained by suitably ad-
iusting or tuning the transmitter
circuit. The amplitude of oScilla-
r.ons is controlled by the value OF
The current in amperes which is per
lnitted to flow through the flament
circuit of the tube.
Oscillatory electrical frequencies
corresponding 10 the frequencies or
ritch OF audible tones or sounds are
employed. and the amplitude OF the
" value which VIII produce sounds
II Predetermined intensity or loud
when circulated through the
windings of the tslepl!one IN the re
electrical energy oscillations general
I'd III the trlnsmitter circuit are I'm
dressed or tho receiver circuit CON
taining the telephone windings
Energy Device Attached.
Associated with the receiver circuit
= an rgy-disSipating device as
we'll as the telephone The energy
dissipating device Is called an at
renuator" This device is adjustable
or variable. and is so connected In
the circuit that any part or all OF the
oScillating electrical current energy
generated III the tran smitted circuit
and impressed on the receiver circuit
can be made TO circulate through It
before reaching the telephone wind
ings.
BY suitably adjusting this device.
therefore. any part or all Of the oscil- =
latory electrical current energy can
he dissipated within this device in
the form OF heat, and consequently
the value of sound-producing energy
which circulates through the tele-
phone windings can be controlled as
desired. and hence the Intensity or
loudneSs of the sounds produced can
IL" regulated as desired. The accous-
tical output from the telephone is