Page 48 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

How do

cordless

phones

work?

How digital cordless
communication became
a household essential

ordless phones are one of those
inventions that are hard to live without.
CPacked with technology, they
originated in the 1980s and were the first
devices to enable landline conversations to
be taken all around the home. Made up of a
handset and a base, the former relies on the
latter to work. The base is plugged into the
telephone jack and receives the incoming call © Corbis; Alamy
as an electrical signal, which it then converts
into a radio signal that it transmits to the
handset. The radio signal gets reconverted
into an electrical signal by the handset,
where it is sent to the speaker and made How do
audible. As you talk into the handset, your
voice is broadcast as a radio signal to the
base, where it is converted to an electrical
signal and sent through the phone line.
Range, sound quality and sound security iceboxes keep
are all essentials, and have got better with
time as analogue frequencies have been
replaced with digital. Some long-range
cordless phones enable you to make and
receive calls even when you are 50 metres (164 food cool?
feet) away from the base station.

These portable chillers save us all from wilting
sandwiches at a picnic, but how do they work?

ceboxes are usually rather ugly looking – liquids or gases), conduction (heat moves
things made out of bulky plastic with a through a substance by particles colliding),
I thick lid. But attractive aesthetics are and radiation (heat is given off and absorbed
sacrificed for good reason – the name of the by an object via electromagnetic waves).
game here is insulation. The walls of an When cold food is placed into the icebox and
icebox consist of multiple layers, filled with the lid is shut, very little heat can reach the
an insulating material such as polystyrene food via convection because warm air from
that is full of air pockets. Air is a poor the outside cannot pass through the box.
conductor of heat, so the gaps in the foam Conduction is also poor because the air
help to slow down the energy transfer of heat bubbles in the polystyrene layer are good
from the outside to the inside insulators. Some iceboxes or cool bags also
of the box. have a reflective outer coating to deflect
Heat is transferred in three different ways: radiation, such as sunlight, away from the
convection (heat moving through fluids precious picnic cargo.

48 How It Works