Data communications are the exchange of data between two devices by means of any transmission medium. The effectiveness of a data communication system depends on three fundamental characteristics delivery, accuracy, and timeliness.
The data must be delivered to the intended device or user.
The data must be delivered accurately i.e. without alteration.
The system must deliver data in a timely manner.
Data communication system
A data communication system consists of five components.
The message is data or information to be communicated. It can be text, numbers, pictures or sound.
The sender is a device that sends data. Various devices can be used to send the data.
The receiver receives the information /message transmitted by the sender.
It is a physical path through which message passes from sender to receiver. The transmission medium can be twisted-pair cable, co-axial cable, fiber-optic cable or radiowaves.
The protocol is a set of rules that governs data communications. The protocol is a pre decided terms for communication.
Direction of data flow
Communication between two devices i.e. sender and receiver can be of three types:
In the simplex mode of communication, data can flow in one direction only (unidirectional). One device can transmit data and another device accepts the data and works accordingly. A typical example of simplex communication is a computer system, data from flow from CPU to monitor or from keyboard to monitor in one direction only.
In the half-duplex mode of communication, each station can transmit or receive the message (data). An important condition in half-duplex mode is that both devices cannot transmit at a time. The entire channel capacity is used by any device transmitting at that time.
In full-duplex mode, both stations can transmit and receive simultaneously. In the full-duplex mode of communication, data flow in both directions share the channel capacity. A common example of full-duplex communication is the telephone network. The subscriber at both ends can talk and listen at the same time.