Every time you make a telephone call—either by dialing or by giving the
operator the number—you first reach the _telephone central office_. This
nerve center of your local telephone system contains equipment through
which your telephone can be connected to any other telephone you wish to
reach.
In a small community there may be only one central office. In large
cities there are many of them, all joined by trunk lines. The term
_telephone exchange_ means the whole local area served by one or more
central offices.
Over four-fifths of all Bell System telephones are dial-operated.
Intricate machinery in the central office makes connections by obeying
the electrical signals that you send over your line as you turn the dial
on your telephone.
Before you dial, the equipment in the central office tells you it is
ready to serve you by transmitting a “hum-m-m-m” over your line. You
should hear this _dial tone_ before you start to dial. The dial tone
serves the same purpose as the operator’s “Number, please!”
[Illustration: _Telephone company buildings are built to harmonize
with surroundings in communities where they are located. A central
office in California._]
[Illustration: _Another one in Connecticut._]
[Illustration: _Testing equipment in a dial central office in a
large city._]
Telephones that are not dial-operated are connected with _manual_
central offices, where operators seated at switchboards make the
connections by hand. Switchboards differ greatly in size. In small
villages one or two operators handle all calls. In large cities the
volume of calls requires hundreds of operators working at large multiple
switchboards. The term _multiple_ comes from the fact that the end of
each subscriber’s telephone line is duplicated or multipled at intervals
throughout the switchboard. For example, a switchboard serving 6,000
customers might have positions for 20 operators. The board would be
multipled so that each operator answering a call from any of the group
of customers assigned to her, could reach his line and connect it with
any one of the 5,999 others.
Written as well as spoken messages are handled through switchboards.
Teletypewriter Exchange Service (TWX) does for the written word what the
telephone does for the spoken word. This service transmits typewritten
messages over any distance through connections made by operators at
switchboards. It is especially valuable for business firms; there are
now some 37,000 listings in the TWX directory.
[Illustration: Typical traffic curve
_City telephones are generally busiest between 9 and 11 A.M., when
business is in full swing. There is another business peak between 4
and 5 P.M. Residence telephones are usually busiest about 7 P.M._]
[Illustration: _Operators, who answer when you dial “O” (operator),
will lend a hand if you need help in calling from a dial
telephone._]
The courteous, helpful service rendered by telephone operators has
become a traditional part of American life. Even in communities that
have dial service, “the voice with a smile” is on the job to handle long
distance calls, to provide telephone numbers not included in the
directory, and to give any other help that customers may desire.
Ever since World War II, the Bell companies have kept on installing new
equipment in great quantities to meet the largest demand ever
experienced for new telephone service.