Data Communication and Networking | Computer Awareness and Proficiency - SSC CGL PDF Download

Types of Signals:

1. Digital Signal: Data is transmitted electronically as binary digits (0 or 1).
2. Analog Signal: Data is transmitted as radio waves, such as in telephone lines.
3. Hybrid Signal: These signals possess characteristics of both digital and analog signals.

Components of Data Communication

When discussing communication between two devices using a network, five key components are essential:

1. Sender: A device capable of sending data over a network, such as a computer, mobile phone, smartwatch, walkie-talkie, or video-recording device.
2. Receiver: A device capable of receiving data from the network, such as a computer, printer, laptop, mobile phone, or television. Both sender and receiver are referred to as nodes in a network.
3. Message: The data or information that needs to be exchanged between the sender and receiver. Messages can be in various forms, including text, numbers, images, audio, video, or multimedia.
4. Communication Media: The pathway through which the message travels from the source to the destination. This medium, also known as a transmission medium or link, can be either wired or wireless.
5. Protocol: A set of rules that the communicating parties must follow to ensure successful and reliable data communication.

Characteristics of Data Communication

1. Delivery: Data must be delivered from the source to the correct destination in the right order.
2. Accuracy: Data must be transmitted without errors. Any inaccuracy during transmission should prompt re-transmission of the data.
3. Timeliness: Data must be delivered within a specified time period, as late data may become useless.

Communication Channel

The communication channel refers to the direction of signal flow between two connected devices. There are three main types of communication channels:

1. Simplex Channel: Data flows in only one direction, with no capability to support a response in the other direction. This type of communication is uni-directional, where one device transmits information, and the other can only receive it. Examples include radio, television, and keyboards.

2. Half Duplex Channel: Data can flow in both directions, but not simultaneously. When one device transmits information, the other can only receive at that time. An example is a walkie-talkie.

3. Full Duplex Channel: Data flows in both directions simultaneously, allowing both stations to transmit and receive information at the same time. An example is a mobile phone.

Communication Media

Communication media, or transmission media, refers to the physical paths that carry information from a source to a destination within a network. It can be categorized into two main types:

Guided Media (Wired Technologies): Data signals are guided along a specific path by a cabling system, which can be composed of metals like copper, tin, or silver. The main types of guided media are:

• Ethernet Cable (Twisted Pair Cable): Wires are twisted together and insulated, with an outer jacket. One wire carries signals to the receiver, and the other serves as a ground reference. Commonly used in local area networks.
• Co-axial Cable: Carries higher frequency data signals through a single inner conductor that transmits electric signals, while the outer conductor acts as a ground. Used in cable TV networks.
  
• Fiber Optic Cable: Made of glass or plastic, it transmits signals as light from one end to another. Optical fibers allow transmission over long distances at higher bandwidths, unaffected by electromagnetic fields, and are much faster than co-axial cables.
  

Unguided Media (Wireless Technologies)

Data is transmitted through waves without using enhanced electrical conductors or wires. Common types of unguided media include:

• Radiowave Transmission: Communication using radio frequencies, ranging from 3Hz to 1GHz. These waves are omni-directional and can travel long distances, especially those that propagate in the sky mode.
• Microwave Transmission: Electromagnetic waves with frequencies ranging from 0.3 to 300 GHz. Microwaves are uni-directional and have higher frequencies than radio waves. Used in cellular networks and television broadcasting.
• Infrared Wave Transmission: High-frequency waves used for short-range communication, ranging from 300 GHz to 400 THz. These waves cannot pass through solid objects and are used in TV remotes and wireless speakers.
• Satellite Communication: Combines radio frequency transmission with satellites to facilitate communication over long distances. Used for communication with ships, vehicles, planes, and handheld terminals.

Additional Communication Technologies

• Bluetooth: A short-range wireless communication technology that allows devices such as mobile phones, computers, and peripherals to transmit data or voice wirelessly over short distances.

Computer Network

A computer network is a collection of two or more computers connected to share information and resources. It involves both hardware and software that enable communication over the network.

• ARPANET: Stands for Advanced Research Projects Agency Network. It was the first network developed by Vint Cerf in 1969.

Benefits of Computer Networks

1. File Sharing: Allows users to share data and files.
2. Hardware Sharing: Enables the sharing of devices such as printers, scanners, CD-ROM drives, and hard drives.
3. Application Sharing: Supports the implementation of client/server applications over the network.
4. User Communication: Facilitates communication using email, newsgroups, video-conferencing, etc.

Types of Computer Networks

• Local Area Network (LAN): A small, single-site network connecting devices over a relatively short distance, such as within a home, office, building, or school. Speed can reach up to 1000 Mbps. LANs are typically owned and managed by a single entity and use technologies like Ethernet and Token Ring.
• Wide Area Network (WAN): A geographically dispersed collection of LANs, often spanning the world, such as the Internet. Speed can reach up to 150 Mbps. WANs use technologies like ATM, Frame Relay, and X.25.
• Metropolitan Area Network (MAN): A network designed for a town or city, covering a larger area than a LAN but smaller than a WAN. Speed can reach up to 100 Mbps. An example is a cable TV network.
• Personal Area Network (PAN): A small network for personal use, covering a limited range. Speed can reach up to 3 Mbps. Examples include Bluetooth, Wireless USB, Z-Wave, and ZigBee.

Network Servers

• Server: A system that responds to requests across a computer network to provide a network service. It is typically run on a dedicated, powerful computer.
• File Server: A type of server that provides access to files, allowing users to share programs and data over a LAN.