~WHAT HAPPENS WHEN WE TELEPHONE~
Mrs. Smith, at “Subscriber’s Station No. 1,” desires to telephone
to Mrs. Jones at “Subscriber’s Station No. 2.” When she lifts her
receiver, the movement causes a tiny white light to appear instantly on
the switchboard at the Central Office. Directly beneath this light is
another and larger lamp, which glows in a way to attract the operator’s
attention immediately.
The operator inserts a “plug” in a little hole on the switchboard
called a “jack,” directly above the tiny light which appeared when Mrs.
Smith lifted the receiver. This connects her to Mrs. Smith’s line. Then
she pushes a listening key on the board, connecting her telephone set
to the line. “Number, please?” she calls.
Mrs. Smith gives the number; the operator repeats it to be sure there
is no mistake, places another “plug” in a “jack” corresponding to the
number of Mrs. Jones’ telephone and makes the connection.
Each subscriber’s telephone has a particular signal on the switchboard
to which it is connected by a pair of wires. Mrs. Smith’s wires run
from her instrument to the nearest “cable terminal,” a gathering point
for the wires of various telephones in her neighborhood. Here they form
part of a group of wires going to the Central Office. These groups,
called cables, are made up of from 50 to 600 pairs of wires, according
to the telephone needs of the district the “terminal” serves.
When the wires reach the Central Office they pass through the “cable
vault” to the “main distributing frame,” which is the Central Office
terminal of the cable.
When the wires come to this frame they are in numbered order in the
cable. Subscribers living next door to Mrs. Smith may have entirely
different call numbers and yet use consecutive wires. It is the task
of the main frame to redistribute these wires, so that they will be
arranged according to their call numbers and to make it possible to
connect Mrs. Smith’s line with the line of any other subscriber with
the least possible delay. This frame has two parts: the “vertical
side” and the “horizontal side.” Before the wires are redistributed
they are taken to pairs of springs equipped with devices for protecting
the lines against outside currents.
[Illustration: ASKING FOR A NUMBER]
After leaving the main frame they are taken to the “intermediate
distributing frame,” the central connecting point for various branches
of the lines going to the switchboard, signaling and other apparatus.
From the “horizontal side” of this frame, wires go to the switchboard,
where they terminate in little holes known as “multiple jacks.” They
also connect with the line and position message registers, where the
calls from each Line and the calls handled at each operator’s position
at the switchboard are recorded. The “multiple jacks” are additional
terminals placed at necessary intervals throughout the switchboard,
where they can be used by operators to make connections with any other
line on the board.
From the “vertical side” of the intermediate frame Mrs. Smith’s wires
reach the “line and cut-off relay,” an electrically controlled switch
which turns on the light signal that appears on the switchboard
when she lifts the receiver from the hook. This “line relay” also
extinguishes the light when the operator makes the connection, or when
Mrs. Smith returns the receiver to the hook.
[Illustration: A TYPICAL POLE LINE, WITH CROSS ARMS, IN THE COUNTRY]
The swift moving electric current that was set in motion when Mrs.
Smith began the call, instantaneously passes through all these devices
for safeguarding and protecting the subscriber’s telephone service. The
light announcing Mrs. Smith’s desire to make a call is called the “line
lamp,” and is flashing on the switchboard. Directly beneath it is the
“pilot lamp,” which glows whenever any “line lamp” lights. With the
“line lamp” is a “jack” or terminal, where connection can be made with
Mrs. Smith’s line. This is the “answering jack.”
[Illustration: THE CABLE VAULT INTO WHICH THE CABLES PASS WHEN THEY
ENTER THE EXCHANGE AND FROM WHICH THEY ARE LED UPWARD TO THE MAIN
DISTRIBUTING FRAME]
When the operator sees the flashing signal of Mrs. Smith’s “line lamp,”
she inserts one end of a pair of “connecting cords,” which are on
the board before her, in the “answering jack” for Mrs. Smith’s line.
These “connecting cords” are flexible conductors that put the wires
of subscribers in electrical connection. Then she pushes forward the
“operator’s key” directly in front of her and is connected with Mrs.
Smith’s line.
The operator ascertains the number wanted and places the other
“connecting cord” in the “jack” corresponding to Mrs. Jones’ line. If
she finds she cannot herself connect with Mrs. Jones’ “jack,” because
it is on another part of the board out of her reach, she makes a
connection with another operator who can reach Mrs. Jones’ line. The
second operator then makes the connection with Mrs. Jones’ “multiple
jack” and places her line in connection with Mrs. Smith’s line at the
first operator’s position. At the same time the first operator pushes
the operator’s key back, thus ringing Mrs. Jones’ bell.
“Supervisory lamps” on the board before her, connected with the
“connecting cords,” tell the operator when Mrs. Jones answers the
summons. They flash when the connection is made and one goes out just
as soon as Mrs. Jones takes the receiver from the hook to answer.
If one of these lamps flashes and dies out alternately it tells the
operator that either Mrs. Smith or Mrs. Jones is trying to attract her
attention and she connects herself and ascertains the party’s wishes.
When both subscribers “hang up,” both lights flash to indicate the
end of the conversation. The operator then disconnects the cords from
the subscribers’ “jacks” and presses the “message register” button
recording the call against Mrs. Smith.
[Illustration: ROUTINE OF A TELEPHONE CALL
The subscriber, after looking up in the directory the desired number,
takes the telephone off the hook, which causes a tiny electric light to
glow in front of the operator assigned to answer his calls. (In some
exchanges equipped with a magneto system, a drop is released by the
turning of a crank.)]
[Illustration: The arrow indicates the light as it appears on the
switchboard. Each operator can connect a caller with any subscriber
in that exchange, but she is assigned to answer the calls of only a
limited number of subscribers whose signals are these lights showing at
her particular position.]
[Illustration: She takes up a brass-tipped cord, inserts the tip,
or “plug,” into the hole, or “jack,” just above the light, at the
same time throwing a key with the other hand in order to switch her
transmitter line into direct communication with the caller, and says:
“Number?”]
[Illustration: The caller replies by giving the name of the exchange
and the number he wants, as for example, “Main 1268.” The operator
repeats the number, “One-two-six-eight,” pronouncing each digit with
clear articulation, to insure its correctness, and, if it be from a
subscriber in the Main Exchange, she--]
[Illustration: Takes up the cord which is the team mate, or “pair,” of
the one with which she answered the caller, locates the jack numbered
1268, and “tests” the line by tapping the tip of the plug for a moment
on the sleeve of the “jack” to ascertain if the line is “busy.” If no
click sounds in her ear she--]
[Illustration: Pushes in the plug and with her other hand operates a
key on the desk. The first action connects the line of the subscriber
called; the second rings his bell. When either party hangs up his
receiver, a light glows on the switchboard desk, showing the operator
that the conversation is ended.]
[Illustration: THE CENTRAL TERMINAL OF YOUR TELEPHONE