The mirror., 1923-11-29
MODERN TELEPHONE EXCHANGE
By Mr.. Il. C.. C..

Mr.. Alexander Graham Bell little real
lied the importance of his invention, our
common telephone while in its experiment
tai stages. With its accomplishment he
has given to humanity great helper. A
silent sentinel, ready day or night, rain or
shine to do our, bidding. 1t must have
been a great pleasure and satisfaction to
have lived and seen the telephone system
grow into one of the largest industries in
the world. To have been able to step into
a modern telephone exchange of today
and know that he was the pioneer of our
great lines of communication.
A grey, almost white, haired man, quite
stout, with a quiet manner and kindly
eye was this great man who passed from
our midst in August of 1922.
To those who have not visited tele-
phone exchange. by all means do so, when
the opportunity presents itself. 1t will be
a source of wonder and educational to
most of us. Little do we realize that
every time we remove the receiver from
its hook, we are setting in motion num-
ber of complex circuits and electrical equip
ment, that the best brains in this and other
countries has to so high degree perfected.
The purpose of this article is to show
what Manual Telephone Exchange con-
sists of, so that the subject will not be too
dry all technicalities are being elimi-
mated as much as possible.
The source of current is usually from
the Power Co. 1t terminates at fuse
panel. From there it goes to the Power
Board where through proper switches and
regulators it is used to drive the motor
generator set. The motor is directly con-
nected by shaft to a dynamo, which in
turn generates current in sufficient guam
tity to charge the storage battery. On
the control panel the current from the dy-
namo is regulated and the battery charged
at its proper rate.
The battery consists of eleven cells,
making twenty-five volts. 1t is made of
a large wooden tank, lead lined so as to
hold sulphuric acid. The plates consists
of the button type made of lead for the
positive plate. The negative plate has
lead grid filled with a composition of
litharge, sulphuric acid and glycerine.
This is what is called the active material.
The storage battery is really the heart of
the system and great care is exercised in
its proper rate of charge and discharge.
Its size depends on the number of sub
scribers and type of equipment it is. to
furnish current for.
The battery is kept in room separate
from other equipment. The reason for
this is that while undergoing charge it
gives off gas. This gas combined with
the air is harmful to other equipment and
also to the health of employees.
From the battery the current is brought
to fuse panel. Each circuit in the ex-
change receives its current through the
fuses of this panel. The fuses are for the
protection of equipment. If short cir
cult or ground puts the circuit out of
operation the fuse blows and automatical-
ly sounds an alarm, notifying the repair
man of trouble. These fuses are of the
grasshopper type and as there are $500
or 5000 circuits in the average good sized
exchange, you will see that there are quite
number of grasshoppers.
All lines or wires come into the ex-
change underground cased in lead cable,
insulated with paper. Some cables have
the enamel insulation. 1900 wires in one
cable are quite common. This type cable
could serve 800 subscribers using the me-
tallic circuit. These cables come from
different sections of the city, which they
are serving. They terminate at the main
distributing frame. Each cable and every
pair of wires are marked for records,
. maintenance reasons, etc. From the hori-
zontal side of this frame these lines are
cross connected no the vertical or multiple