Page 252 - DK Children's Encyclopedia

Telephones SEE ALSO

▸ ▸ Codes pp.66–67
▸ ▸ Communication
Telephones allow people to speak to each other from p.69
anywhere in the world. They turn the sound of our ▸ ▸ Computers p.71
voices into signals, which are sent through radio waves ▸ ▸ Electricity p.87

or cables to another phone. That phone then changes ▸ ▸ Hearing p.127
the signals back into sound. ▸ ▸ Internet p.138

Where does
your voice go?
When you speak into a
phone, the sound of
your voice is turned
into electrical signals.
A network of telephone
lines and cell towers let
us speak to people over
long distances.

Cell tower Telephone lines
These towers send and Phone lines carry phone
receive signals between signals long distances by
mobile phones and a holding the wires up
telephone exchange. above the ground. For
longer distances, cables
can even go underwater.

Mobile phones Telephone exchange Wired phones
Mobile phones send and receive signals This place connects telephone calls Landline phones have a cable that
as radio waves. They don’t work if they using computers. It sends incoming plugs into a wall. They send a
are too far away from a cell tower. signals to the right phone. signal through a network of wires.

Past and present 18:05 Smartphone
The way that phones send and receive Tuesday, 20 April A smartphone is a
signals has changed since they were first pocket computer
invented. Early telephones sent sounds that can be used
short distances through pipes or tubes. to make phone calls,
From the 1800s, telephones sent electrical record videos, and
signals through wires. Mobile phones use First telephone play games.
The telephone was invented in 1876 by
radio waves to pick up signals. Alexander Graham Bell, a Scottish music teacher.

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