CHAPTER 3 Data Communication.pdf

DATA The collection of raw facts and figures is called data. The word data is derived from the Latin language and it is plural of Datum. The text, numbers, symbols, images, voice, and video which are processed by computers and digital devices are called data. Data can be considered as unprocessed information. COMMUNICATION Communication is the process of sharing a message. A conversation between two people is an example of communication. DATA COMMUNICATION Data Communication is the process of transferring data electrically from one place to another. It is the process of exchange of data and information between two parties such as humans and electronic or computing devices. COMPONENTS OF COMMUNICATION SYSTEM A Communication system has the following five components. Message It is the information or data to be communicated. Common forms of information include text, numbers, pictures, audio, and video. Sender It is the device that generates and sends a message. It can be a computer, telephone handset, etc. Receiver Any particular digital electronic device can receive data in form of a message. The location of receiving computer is generally different from the sending computer. Like the sender, it can also be a computer, telephone handset, etc. Medium It is the channel or path through which the message is carried from the sender to the receiver. Some examples include twisted-pair cable, coaxial cable, radio waves, etc. Protocol Protocols are the rules and procedures by which computers exchange data on the network. The sender and receiver follow the same protocols to communicate with each other. In other words, a protocol is an agreement between two parties or vendors, using communication devices. STANDARDS Standards are the set of rules for data communication that are needed for the exchange of information among devices. It is important to follow Standards that are created by various Standard Organizations like IEEE, ISO, ANSI, etc. CHARACTERISTICS OF DATA TRANSMISSIONS Data communication has several characteristics but some are discussed below: 1.Signal type 2.Transmission mode 3.Direction of transmission 1.SIGNAL A signal is an electromagnetic or electrical current that carries data from one system or network to another. TYPES OF SIGNAL There are two types of signals discussed below: Analog Signals Analog signals are continuously varying signals or waves that change with time and are used to represent data. Characteristics Of Analog Signals Amplitude The amplitude of a signal refers to the height of the signal. It is equal to the vertical distance from a given point on the waveform to the horizontal axis. It is measured in volts. Frequency Frequency refers to the number of periods in one second or the number of cycles per second. Frequency is measured in Hertz (Hz). Digital Signals A digital signal is an electrical signal that is converted into a pattern of bits to represent a sequence of discrete values, at any given time.Read less