The times dispatch. [volume] (Richmond, Va.) 1903-1914, 1906-08-02
Z thousand Mile Talks
on a Three-F DOT Line
How Engineers Are Planning and Perfecng the Telephone
System Of To MorroW-A Unique Laboratory that
Does Its Work All Over the United States
Experiments and investigations that Z
Look Twenty Years Ahead.
Special to The Tlmes-Dispatch.)

Especial to The Times Dispatch)
August lin a skyscraper OF
flee building in8this city is one OF the
busiest and most interesting laboratories
in the world. 1t is the place where the
problems $of telephony are worked out,
and where are devised the means OF I'M m.
4 proving and developing the national talk talk
ing system to meet the demands inc
future will make upon It. @
g{5 Here, any day. you may see two men
in q room Is or 20 feet wide and two or
three times that LENGTH talking with
each other over circuits = a thousand
miles long. The equivalent Of twenty
miles Of cable Is contained In box no
bigger than an ordinary travelling Dag,
and 600 miles Of pole line is represented
B by the contents Of another box mot; as
large as q dress suit case. while. the en-
tire apparatus at the central office, SO
far as 1t II affects the Individual sub.
scriber's telephone line, Us compresse
Into couple OF square feet.
81 With this equipmen 4 and two e stand
gardized telephone instruments conYersa-
ations over hundreds Of miles are carried
on within the four walls Of this labora-
$tory-one Of the rkshops OF the central
engineering force OF the Bell s. system.
Every detail of&a long distance circuit
from the Subscribers telephone at one
end Of the line to- that atathe other end,
with all the centralt OF fce and overhead
and underground construction that con-
meets them, Is reprodu cetl with X scien-
title exactness. Byfthese means .new&de
vices and apparatus are tested, proposed
improvements investiga ted, W. and By the
scientific theories involved I'm transmits
sion and operation worked outs This may
be done for the purpose Of studying some
minor BIT Of mechanism, OF determining,
for Instance. the rela tive merits Of two
forms Of the relay. coils n which auto
1natically5 work the signals on the switch
board, or Of learning the effect on q
conversation Of having one sort Of equip
I1lent at one end OF the line and another
sort at the other end, or for any OF
hundred other purposes. t58a "A
Il: The way in which! tests Of this sort
are made is curious. At one end OF tho
$labora tory is telephone instrument that
Is kept at an absolute standard. Half
way down the room Is @ sound-proot
booth in which a similarly perfect in
strument is Installed The telephone In
the open room has practically the SUR
Broundings Of the ordinary subscribers
premises: the other Is secluded SO as to
give as nearly absolute quiet as possible
Il and allow the trained ear6to judge COR
rectlys the sounds that come over the
wires. On q shelf beside each telephone
stands a device which, by shifting It's
keys and changing Its electrical resist
ance, can be made to represent the loop,
as 1t lis called, between the subscribers
station" and the central office. Fast
ened to the wall are repeating coils, re-
lays. and condensers exactly like those
attached to every SUBSCRIBER line IN q
regular exchange II
The devices that represent that out
side lines Of the telephone system,
whether cable under city streets, or open
wire on pole lines, are the most inter-
gesting Of all. They look like boxes two
or three feet long and six inches wide,
with double line Of electrical switches
on the top. Inside each box Is a series
Of contrivances each with the electrical
resistance and capacity Of SO much cable
or wire, as the case may bel and by
number Of the sections Of artificial 3line,'
as they are called, can be put into the
circuit under test The artificial lines
are made by taking the resistance Of the
size OF wire they are to represent, allow
ing for the inevitable leakage OF current
under some conditions and for the In
stluence of Induction under others, and
then embodying the results In "a single
compact device which Will produce on
any current that Is passed through 1t the
combined effects of all these various
influences. ~ gi
When the engineers wish to compare
the efficiency Of two pieces Of apparatus,
each is connected with the same wires
through mercury SWITCH" The
switch can be worked so as to put first
one Of the samples under examination
and then the other into the test circuit,
One observer talks into the instrument
at the open end OF the line. rocking the
switch hack and forth, while the other
listens In the sound-proot booth. noting
the differences In transmission caused
by each change OF oonnections-differ-
ences which to the unframed ear would
aba hardly perceptlble Sometimes an
actual operating plant is compared with
standard equipment like that used in
the laboratory, by means OF one oftthese