F.B. Morse worked on a telegraph of
his own. Morse developed a new system
for sending telegraph messages. It used
dots, dashes, and spaces to stand for
letters and numbers. This system is
called Morse Code. Morse and his partner,
Alfred Vail, built a telegraph with
just one wire. The transmitter had an
arm called a key. The person sending the
message pressed the key to tap out messages
in Morse Code.
In 1843 the U.S. government paid
Morse to build the first long-distance
telegraph line. It ran 35 miles (60 kilometers)
fromWashington, D.C., to Baltimore,
Maryland. The next year Morse
sent the first message through the system.
The message was “What hath God
wrought!”
The Telegraph Industry
Morse’s telegraph started an entire
industry. By the end of 1861 a telegraph
line ran all the way across the United
States. By the end of the 1800s telegraph
lines crisscrossed the world. In the early
1900s a new kind of telegraph could
print out messages. Later telegraphs
could send messages through the air
instead of through wires. The wireless
telegraph was an early form of radio. By
the end of the 20th century the tele-
The telegraph invented by Samuel F.B.
Morse had a key for tapping out messages.
BRITANNICA STUDENT ENCYCLOPEDIA Telegraph 35
graph had been mostly replaced by faster
communications that used computers.
#More to explore
Electricity • Morse Code • Radio
• Telecommunication
Telephone
The telephone is a very common device
for communicating over a distance.
With a telephone, a person can talk
almost instantly with someone on the
other side of the world. Most telephones
are linked to each other by wires. Others,
such as cell phones, are connected
by invisible radio waves that travel
through the air.
How a Traditional Telephone
Works
A traditional telephone depends on
wires to send sound. It has a handset
and a base that are connected by a cord.
The handset is the part that a person
holds to make or answer a call. One end
of the handset has a microphone for
talking. The other end has a small loudspeaker
for listening. The base connects
the telephone to an electric current
through a wire.
When the caller speaks into a telephone,
the microphone changes the sound of
the person’s voice into an electric signal.
The base sends out the signal through its
wire. How the signal travels from there
depends on where the call is going. It
can remain an electric current, passing
through wires and cables. It can travel
through thin glass fibers in the form of
light. This way of sending information is
called fiber optics. Or the signal can be
changed into radio waves and sent
through the air by antennas and satellites.
When the signal reaches the telephone
at the other end, its loudspeaker
changes it back into the sound of the
caller’s voice.
Cordless Telephones
A cordless telephone is more convenient
than a traditional telephone. It does not
have a cord connecting the handset and
the base. It allows a person to walk
around the house while talking.
A cordless telephone uses both electric
signals and radio waves. The base
receives the call as an electric signal, like
a corded phone does. Then the base
turns the electric signal into radio waves.
Using an antenna, the base sends the
waves through the air to the handset.
The handset’s antenna picks up the
waves. Then the handset turns the waves
back into sound.
Cell Phones
Cellular telephones, or cell phones, are
even more convenient than cordless
phones because they work over a much
wider area. Because of this, in some places
they are called mobile phones. They send
and receive calls using radio waves.
Cell-phone companies divide up an area,
such as a city, into sections called cells.
Each cell has a tower for receiving and
sending out radio waves. If a caller travels
from one cell into another, the call
switches from tower to tower. This
means that a cell phone can work any-
The word
telephone
comes from
the Greek
words tele,
meaning “far”
and phone,
meaning
“sound.”
36 Telephone BRITANNICA STUDENT ENCYCLOPEDIA
place that the cell-phone company’s
network reaches. Cell-phone networks
can stretch across an entire country.
A cell phone sends out a special signal
whenever it is turned on. The signal lets
the network know where to send the
calls that come to that phone.
Many cell phones can do things other
than make calls. Certain kinds can get
information from the Internet or send
and receive e-mail. Some cell phones can
take photographs.
History
Not everyone agrees who invented the
telephone. However, Alexander Graham
Bell usually gets the credit. In 1876 he
sent the first words by telephone. Later
that year Bell made the first longdistance
call. He talked with his assistant,
who was 2 miles (3.2 kilometers)
away. By 1915 people could place telephone
calls across the United States.
Telephone service across the Atlantic
Ocean began in 1927. The first cell
phones appeared in the late 1970s.
Telephones had no dials in the
first part of the 1900s. Instead of
dialing, callers told a telephone
operator the number they
wanted to call.
BRITANNICA STUDENT ENCYCLOPEDIA Telephone 37
In some reflecting telescopes light passes
