Cellular Phones

by Juhan Rebane 2005

Topics What is a cellular phone ? How it works ? What do it consists of ? Student´s consumption . What do students think about possible

threat to environment and health ? Possible threats to environment and

health .

What is a cellular phone ?

Basically it is a radio . It enables you to change information

(speech, data etc.) Nowadays the function of cellular

phones is more sophisticated . There are phones that look more like computers or cameras than phones .

Haier PenPhone

Qtek 2020i

How it works ? Cellular phone technology works on a

system of geographically separated zones called "cells."

Each cell has its own "base station" that both receives and emits radio waves.

When a call is placed from a cellular phone, a signal is sent from the cell phone antenna to that cell's base station antenna.

How it works ? The base station responds to the cellular

phone signal by assigning the phone an available radio frequency channel.

When the RF channel is assigned, modulated radio signals are simultaneously received and transmitted, allowing voice information to be carried between the cell phone and the base

How it works ? The base station transfers the call to a

switching center, where the call can be transferred to a local telephone carrier or another cell phone

Cellular phones operate with radio frequencies, a form of electromagnetic energy located on the electromagnetic spectrum between FM radio waves and the waves used in microwave ovens, radar, and satellite stations.

Electromagnetic Spectrum

What do they consist of If you take a cell phone apart, you find that

it contains just a few individual parts: An amazing circuit board containing the brains of the phone An antenna A liquid chrystal display (LCD) A keyboardA microphoneA SpeakerA battery

The microprocessor The cell-phone speaker, microphone and battery backup

The front of the circuit board

Consumption It is assumed that there are about 1.6

billion cell phones all over the world It is assumed that there are about one

million cellular phones in Estonia . Most of our high school students have

cellular phones . We had a survey – 49 studets had and only

1did not have a cellular phone .

How often high school students buy a new cell phone

86

10 40102030405060708090

100

after couple ofyears

every year several times ayear

percent

Reasons for changing cell phone

56

8 1634

0102030405060708090

100

old one isinoperative

access to thenewest model

access to newertechnology

access to newerphone although

old one isoperative

perc

ent

Consumption

Most of students monthly consumption is between 100 – 300 EEK (6 - 18€)

90 % of students use SMS 18 % of students use MMS 22 % of students use WAP/GPRS

What students do with old cellular phones ?

10

46 44

0102030405060708090

100

throw away keep them takes them toshop

perc

ent

Student´s opinion is that cellular phone technology is … to health and environment .

4

52

1430

0102030405060708090

100

absolutly safe has no seriouseffect

very dangerous had no opinion

perc

ent

Possible threats to environment and health

Current scientific evidence indicates that exposure to RF fields, such as those emitted by mobile phones and their base stations, is unlikely to induce or promote cancers

Scientists have reported other effects of using mobile phones including changes in brain activity, reaction times, and sleep patterns. These effects are small and have no apparent health significance

Possible threats to environment and health

Driving: Research has clearly shown an increased risk of traffic accidents when mobile phones (either handheld or with a "hands-free" kit) are used while driving.

Electromagnetic Interference: When mobile phones are used close to some medical devices (including pacemakers, implantable defibrillators, and certain hearing aids) there is the possibility of causing interference .

Possible threats to environment and health

Near some base stations the RF fields exceed exposure limits .

Current mobile phone systems operate at frequencies between 800 and 1800 MHz. It is important not to confuse such RF fields with ionizing radiation, such as X-rays or gamma rays. Unlike ionizing radiation, RF fields cannot cause ionization or radioactivity in the body. Because of this, RF fields are called non-ionizing .

Used links

www.who.com www.howstuffworks.com www.germandia.ee

Electromagnetic Spectrum