The concepts central to the communication process are:
Serial and parallel
Simplex, half duplex and full duplex
Synchronous and asynchronous
Each concept describes a characteristic that must be agreed upon for successful communication to occur. These characteristics underpin the operation of hardware and software used for transmitting and receiving.
Serial transmission can be likened to a single lane road.
Parallel transmission is more like a multi-lane road.
Today parallel transmission is rarely used for communication outside of an individual computer. The majority of computer systems only use parallel communication between components that are part of the motherboard or are connected directly to the motherboard. In the near future it is likely that computers and printers will not contain parallel ports at all.
Parallel transmission is significantly faster than serial transmission. However, parallel transmission is only ever used over small distances.
There are problems related with parallel transmission:
There are many more wires required for parallel.
The extra cost becomes more significant as the distance increases.
Data must be assembled into groups equal to the number of parallel wires.
In our multi-lane road, as the length increases, it becomes harder for the cars to remain precisely side by side so the result in a computer is that not all bits arrive at the same time. – ‘Data skew’
Serial transmission can be either asynchronous or synchronous.
In Asynchronous transmission, each byte is identified with special start and stop bits. In asynchronous transmission, there is only one wire/signal carrying the transmission. This has become the standard for personal computers providing connectivity to printers, modems, fax machines, etc.
Synchronous transmission requires all data to be sent at the same rate. It is faster and more efficient than asynchronous transmission, and is used on larger computer systems.
Half duplex means that communication can occur in both directions, but never at the same time. For example a walkie talkie, operates in half-duplex using a single channel. In an IPT situation, this can be associated with working on the server as you can open and save documents on the network but never at the same time. Also like a single laned bridge.
Full duplex mode Full Duplex mode Both ways simultaneously
The speed of data transfer is measured either by its baud rate or by the number of bits per second (bps).
Baud rate is a measure of the maximum number of data symbols or electrical signals that can be sent per second over the communication link.
Bits per Second (bps) is a measurement for the speed of data transfer. Bps is an indication of how many bits pass a certain point in one second. The larger the bps/ baud rate the faster the download and/or upload time will be
A modem is a device that enables data to be transmitted from one computer to another. The word modem stands for mo dulator/ dem odulator. This is because a modem converts (modulates) digital signals sent from a computer into analog signals, suitable for transmission on a telephone line. Analog signals are pulses in the form of waves. They can be either electrical pulses, or light pulses. When the signal is received by another modem, it reverses the process by converting (demodulating) the analog signal into a digital signal suitable for the receiving computer.
Modems can be internal or external.
Internal modems are a type of expansion card fitted into an expansion slot inside the system unit. They have become quite popular because they do not occupy much desk space.
External modems are usually connected to a serial port and require a power supply and take up some desk space. They have a set of status lights to indicate what the modem is doing, and are generally more expensive than internal modems.
For example: The Creative Modem Blaster (internal modem) : $45
A Open FM56-EXV (External Modem): $63
The speed of a modem is measured by bps or the baud rate. Because of the speed limitations of modems, many users are upgrading to a broadband connection such as a cable modem or DSL, which offer a faster download and upload speed when compared to the modem.
When a number of peripheral devices are connected, it is called a network. The simplest form is when one computer is directly connected to another computer using a cable. However it can often consist of hundreds of computers connected together.
The devices used to send data to a computer system or receive data from a processor are called terminals. They can be dumb, smart, or intelligent.
Dumb terminals do not contain a processor and usually consist of a keyboard and monitor.
Smart terminals can do some low-level processing such as text editing.
Intelligent terminals have both memory and processing capabilities.
Networks are classified according to the distances they cover and include local area networks and wide area networks.
Local Area Networks (LANs) connect computers within a building or group of building on one site. They are found in offices, hospitals, schools and tertiary institutions.
Wide area networks (WANs) connect computers over hundreds or thousands of kilometres. They often consist of a main computer system called a host and a number of terminals. WANs are slower than LANs at transferring data because they are not directly connected.
All Application software transmits and receives data within an individual computer.
Communications software manages the data, files and commands between computers. It uses protocols to establish a connection. It defines how the information is transmitted and how errors are detected. There are a number of different protocols for networks with the most popular being: Ethernet and Token Ring
Compression software reduces the number of bits required to represent data. It compacts the data so that it takes up less space on a disk and requires less time to download. Compressed data must be decompressed in order to extract original information. Example, WinZip
Electronic mail (email) allows communication with other users by sending and receiving electronic messages using a computer. Email messages are often short and are typed quickly. Example, Hotmail, Yahoo! Mail
Data Encryption is used to prevent data from being intercepted and read during transmission. The data is ‘scrambled’ so that it is meaningless to anyone other than the recipient, who uses the same encryption software to convert it back. Example, Cypherus, Crypkey
Non-computer tools used to transmit and receive include:
The mail system : This makes it possible to send a letter or package to the address of any person around the world. The delivery of mail is dependent on road, rail and air transportation systems. Mail systems have improved steadily, especially with the development of machines that can sort letters. These advances in technology mean that there are now faster methods of postal handling and delivery.
The telephone system transmits sounds or speech between distant places along telephone lines. It is a convenient method of communicating with people around the world.
Fax machines transmit and reproduce documents by mean of signals sent over telephone lines.
Radio is the transmission and detection of sound using electromagnetic waves that travel through the air. It remains a popular form of communication but it is restricted to a one-way transmission of data.
Television is the transmission and detection of images and sound using electromagnetic waves that travel through the air. A scene to be televised is translated into a sequence of electrical impulses that are transmitted via an antenna. Television has recently become interactive with Foxtel Digital, and this means that it is now capable of two-way transmission.
The widespread use of information technology has raised a number of ethical issues for people.
As it is so easy to publish information on the internet, the accuracy of the information received from the internet is not guaranteed.
The security of data transferred over the internet is a great problem. One method to protect data from deliberate or accidental damage is by using a certificate, this will have a digital signature that is an encrypted code and it will identify a particular person or website so that unauthorized persons may not access it.
Communication over the internet or ‘Netiquette’ is compromised when users send inoffensive messages, do not infringe copyright or have respect for the privacy of other users.
Acknowledgement of sources is necessary when downloading data and it is protected by copyright.
In some areas of employment , the information systems have improved the nature of work and allow workers to learn new skills. However, it may also have the reverse effect and some people’s jobs now require fewer skills (deskilling).
The Internet is also having an impact on traditional businesses as many are trading entirely online and using websites to promote their goods and services. This means that the traditional businesses that provide an opportunity for human interaction are being challenged.