The New York herald., 1922-03-12
America Starts Back to Bremen
and Will Continue Her
Phone Experiments.
WONDERS OF THE DUPLEX
Talking and Listening Over
Sea and Land at the Same
Time Is Accomplished.

history, as did her last trip, when,
hundreds OF miles out at sea, those on
board talked with people ashore in their
own homes.
Although II had been planned orig
inally to make only one return voyage
to test the new duplex telephone set,
the remarkable results caused William
H. Rossbottom, general manager of the
line. to urge that the set remain on the
ship and engineers Of the Radio Cor
poration OF America and the General
Electric Company sailed with her.
From shore other engineers, including
those at the American Telephone and
Telegraph radio stations at Elberon and
Deal Beach. n. j., will take part in the
tests.
The Importance of the present expert
ments is the fact that the duplex tele-
phone set on board. developed at cost
of many thousands of dollars and
years work, is looked upon as likely
TO make long distance radio telephony
both simple and practical The big
feature of the duplex set is that with
1t person can talk and listen at the
same time, without operating any
switch or push button, just as at an
ordinary telephone.
One of the most unusual features the
new development will make possible will
be tried out on this trip when Capt. VIII
liam Rind OF the America, at his post
on the bridge of his ship, will en-
deavor to be In touch in midocean
with Mr.. Rossbottom In the offices OF
the line in New York, and will be
connected with others at their homes
and offices through the regular tele-
phone connection.
Experiments VIII Continue.
During the entire trip the engineers
on the America. I. F. Byrnes Of the Gen
eral Electric Company, who Is largely
responsible for the development of the
duplex set. and Karl Macnvain of the
Radio Corporation, will continue the ex-
periments made last trip by Mr. Byrnes,
T.. V. Amy of the Radio Corporation and
j. +. Harrington OF the Western Electric.
On Thursday night, when the America
Il 1000 miles from this coast, an effort
will be made to hear Charles p. Stein
metz. the electrical wizard" Of the Gem
eral Electric Company, who will talk on
the broadcasting set of his company at
Schenectady, Station WGY, on 800
meter wave length. After Mr.. Steinmetz
has completed his talk the America will
endeavor to reach him by telephone.
In addition to these tests. much of
the regular radio traffic on the ship will
be sent out by radiophone and selections
by the Americas orchestra broadcasted
to ships not carrying musicians. 4
Before the tests made last Sunday,
when II. =. Thayer. president of the
American Telephone and Telegraph Com
pany, from his home at New Canaan
talked with Capt. Rind. $40 miles away,
,f.y f1ut
formed. This was a radio conversation
between one OF the engineers on board
the America. with his wife, almost a
thousand miles away. at the home OF
Carl Englund, a radio engineer OF the
Western Electric Company. over the or
binary telephone wire. Long Branch
426, party NJ. This conversation passed
through the station ut Deal No such
land line connection with n distant radio
phone had ever been attempted before
One OF the most serious difficulties
ahead OF duplex telephony. the expert
menters found, was the spark" inter-
ference on 450 meters This is due to
the fact that spark" sets OF ships send
Ing on $50 metre wave length actually
are so broad that they cannot be tuned
out of q radio telephone set operating on
410 meters. When this spark type was
sending near the America IL was not
possible to ''get" the conversation from
the Deal station. which at no time went
higher than s20 meters. Ships at the
present time are licensed to send on 600,
$50 and 800 meters. Usually they use
the 900 meter wave length. but when
there IS considerable traffic at this
length they drop to 450 or thereabouts.
1t Is then that they jam the telephones.
Spark Only Bothersome Thing.
The CIV transmitter continuous
wave) on ships did not bother the
America as did the spark. The radio
amateur down at 200 metres, did not
interfere either. The log shows that al
most all the trouble was from spark In
reference. This trouble viii diminish
as more and more ships adopt the mod
ern CIV transmission.
Prior to this recent experiment In the
duplex system of radio telephony. and
others by the Western Electric, wireless
telephony was carried on by the simplex
or push button system.
Concerning this system Ernst r. W.
Alexanderson, chief engineer OF the
Radio Corporation. said more than flve
years ago:
Everybody who has experimental
with radio telephony has undoubtedly
observed that the Interchange OF ideas
is not satisfactory IL IL is necessary to
manipulate n switch Of some kind Cor
push button) in order to change the
equipment from sending TO receiving
Even liz an automatic device IS used for
performing the change over the two
parties are apt TO say hello simultanc-
ousiy, then wait for an an.wer stimuli
taneously, then say. hello again, and
finally give It up in despair. II can
therefore be said that one OF the most
important problems from the point of
view OF making radio telephony practical
and useful for the general public is TO
devise n simple method OF duplex oper-
alton whereby the speaker IS able to
hear the voice of the other party In the
same way as this is done on the wire
lines"
In The present set this duplex opera
tion is accomplished by using the same
antenns, but different wave lengths, in
talking and listening, n length of 355
for tho former IN tho recent tests on
tho America, and OF 40 for the latter.
A trap Ia used TO filter out the energy
% the local translnitter from the re-
ceiver.
The transnitter Is rated at T5o watts,
developing twelve amperes In the ships
antenna. Actually the transmitter de-
veloped an output OF 500 watts. Tho
transmittcr, which Is in two parts, the
power unit and the generating coll sys-
\ tenn, il about six feet high, two and one
half feet broad, and two feet deep. It
weighs about three or four hundred
pounds.
During the tests on the present voyage