Information and Communication Technology (ICT) is a board term which covers all advanced technologies used in manipulating and communicating information.
ICT encompasses all medium to record information, the technology to broadcast information and to communicate information. Its range varies from the home user to the largest global network.
Communication of data and information plays a vital role in the functioning of any organisation with the growing use of computers everywhere.
Data Communication is a process of sending data electronically from one geographical location to other, which is usually done by linking different locations using a network.
Networking not only helps in data communication but it also permits the users to share the available resources, update the data and analyse it.
Communication Channel is the medium used to convey information from a sender to a receiver. When data is to be sent from one computer to another, it is first converted into electromagnetic energy to send it to another computer using communication channel.
The communication channel is carried over a transmission medium. Such media can be wired, as in the cases of twisted pair telephone wires, co-axial cable or can be wireless, such as radio, satellite.
We will discuss about Analog transmission and Digital transmission here:
§ An Analog Signal is a continuous signal whose amplitude, phase or some other property varies in a direct proportion to instantaneous value of a physical variable. There is a continuous up and down pattern. One wave constitutes on cycle, which is measured in the unit called Hertz. All telephone calls are used to be transmitted in an analog format.
§ In Digital Transmission Signals are discontinuous that charges from one state to another in discrete steps. A popular form of digital modulation is binary, or two level digital modulations. An example of digital is data stored in the memory of a computer is the form of 0s and 1s. It is usually converted to a digital signal before transformed.
Modem stands for Modulator Demodulator. It is a communication device that modulates signal in order to encode digital information so that it can be easily transmitted and afterwards demodulates it to reproduce the original data.
Basically it converts digital data into Analog data and vice versa. When there is one standard interface for connecting external modems to computers called RS-232, any external modem can be attached to any computer that has an RS-232 port.
How Modem Works?
When a modem first makes a connection, it produces sound. Basically these are the digital signals coming from the computer to which you are connecting being modulated into audible sounds.
To represent the digit 1 modem sends a higher pitched tone and for digit 0 a lower pitched tone is used. At the other end of your modem connection, the computer attached to that modem reverses this process. The receiving modem demodulates the various tones into digital signals and send them to the receiving computer.
The actual process is much more complicated than it seems. There are some internal functions like Data Compression, Error Correction, Flow Control and Data Buffering that helps in modulation and demodulation process.
The directionality of the information can be either one-way or two way. The message source is the transmitter and the destination is the receiver.
§ Simplex Channel: A channel whose direction of transmission is unchanging is referred to as a simplex channel. Here only one way communication is possible. Example is radio and TV broadcasting. In this mode there is just one way communication channel. So, we can receive data on that channel but could not be able to transmit on same channel.
§ Half Duplex Channel: A half duplex channel is a single physical channel in which the direction may be reversed. Message may flow in two directions, but never at the same time, in a half duplex system. For example: Walkie – talkie
§ Full Duplex Channel: A full duplex channel allows simultaneous message exchange in both directions. It really consists of two simplex channels, a forward channel and a reverse channel, linking the same points. Example is Telephone Communication; we can listen and talk at the same time on telephone.