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UNIT 16
Communications Systems
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Introduction
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Introduction
• Mobile phones have become
a common way of
communicating. They are small computing devices in the
form of a telephone handset that can connect to local radio
networks allowing users to make normal telephone calls.
• They have extra HW and SW features including:
1) Keyboards
2) Earphones
3) Phone book in the form of a database storing telephone
numbers.
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Introduction
4) Text messaging that allows short messages to be transmitted and
received.They are displayed on a small screen built into the handset.
5) Calls register that stores details of any telephone calls that are sent
or received or missed.
6) Computer games programs that can be downloaded and played on
the handset.
7) A program that allows the handset to be used as a mathematical
calculator.
8) An alarm call facility that automatically causes the handset to ring or
a message to appear on the screen at a time chosen by the user.
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Introduction
• When sending text messages, abbreviations consisting of
letters and numbers are used to save typing and to make
it easier to display the messages on the small screen e.g.
CU L8R is commonly used to represent ‘see you latter’.
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Introduction
• VoIP (Voice Over Internet Protocol) is a set of
standards for enabling phone calls to be made across the
Internet:
▫ It digitizes the voice signal (converts the analogue wave
into a digital pulse).
▫ Then it compresses it using a codec ( coder/decoder, a
program used for converting sound and video signals for
use in a computer).
▫ It is then broken down into packets (small, fixed sized units
of data).
▫ It uses a buffer to reduce jitter (differences in the time
packets take to arrive at their destination).
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Introduction
▫ ITSP (Internet Telephone Service Providers) companies
provide gateway systems that enable computers to be
connected to the ordinary telephone system.
▫ A new type of spam (unsolicited emails) is likely to
appear on VoIP systems. This is known as Spit
(unsolicited telephone calls made using VoIP on the
Internet).
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Introduction
• In the future, computers will become more powerful.
They will be faster and with bigger storage and
processing capacity.
• They will also become cheaper to produce so they will
be more commonly available and allow them to be
integrated with other devices such as video recorders,
TV’s and telephone systems.
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Introduction
• Cheaper and more compact, flat digital panels are likely
to be used for monitor screens in the future and security
will be provided by biometric devices rather than
passwords i.e. devices that measure some aspect of a
living being such as eye scanning devices or fingerprint
recognition devices.
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Introduction
• It will also become cheaper and more common to print
photographs from a camera using a color laser printer.
• Flexible motherboards (the electronic circuit boards
that hold and connects the main parts of a computer)
will allow the design of computers to be more varied in
the future.
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Introduction
• Voice control will allow the user to input data and
control the computer by speaking.
• In the future, SW will be rented and run across the
Internet rather than being bought and installed on
individual computers. They will be built into clothing and
worn by the user.
• Domestic appliances such as fridges and cookers will be
computer controlled.
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Introduction
• In the longer term, computers may be operated using
laser light or quantum physics rather than electronics
and may even be implanted into the user’s body, even
into the human brain. This may help people with
disabilities.
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Introduction
• Computer-mediated communication (CMC) can be
either :
▫ Synchronous, where the users can communicate with each
other at the same time in real-time, i.e. immediately,
enabling interactive communication.
▫ Asynchronous, where messages are sent to a user who
receives them and replies at a different time.
• Some messages are text only, some are audio only and
others are multimedia (include text ,graphics, audio,
animation and video data).
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Introduction
• A pager is a small radio receiver which beeps to alert
the wearer of messages or telephone calls. It displays the
phone number of the caller so the wearer can call back.
Some pagers can display very short messages.
• A bulletin board is an electronic notice board system
that enables users to display messages for other users to
read.
• A MOO system is an Internet virtual environment,
developed for multi-user adventure games, that allow
many users to interact in real-time.
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Introduction
• A GPS receiver (Global Positioning System) uses a
microprocessor (the main electronic chip in the
computer that does the main processing and controls
other parts of the computer) to compare coded digital
signals ( an electronic signal that has only two states on
and off) from special satellites orbiting the earth to
calculate latitude, longitude and altitude and enable the
user to determine their exact location.
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Introduction
• Extremely accurate atomic clocks are used in the
satellites.
• GPS systems, although originally developed for the US
military, can be used for a variety of purposes including
orienting hikers, navigation ships, tracking trucks and
buses and locating stolen cars.