Communications Systems UNIT 16 Communications Systems

Introduction

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: Keyboards Earphones Phone book in the form of a database storing telephone numbers.

Introduction Text messaging that allows short messages to be transmitted and received. They are displayed on a small screen built into the handset. Calls register that stores details of any telephone calls that are sent or received or missed. Computer games programs that can be downloaded and played on the handset. A program that allows the handset to be used as a mathematical calculator. 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.

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’.

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).

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).

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.

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.

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.

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.

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.

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).

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.

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.

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.