Principles of Information Technology Chapter 23 Communications Basics

Principles of Information Technology Chapter 23: Communications Basics

Communicating by Telephone § Sending information over a telephone network is called telecommunications. § Telecommunications can be duplex, where the people on both sides can communicate at the same time, or half -duplex, where only one side can communicate at a time.

Making Telephone Calls § Telephones connect to a common network, called a local loop, for service within a neighborhood. Much of the local loop is an analog system, which sends electrical signals that carry voice and other sounds. § Digital connections use computer code and can carry voice, data, and video on a single line. § Many phone calls are made through the Public Switched Telephone Network, which is built from copper wires and other cables and forms a circuit between the caller's telephone and another telephone.

Wired § The telephone system used to depend on twisted pair technology, which refers to a pair of copper wires that are twisted together to reduce interference, or outside noise. § Fiber-optic cables are strands of fiberglass that transmit digital data by pulses of light. § Before fiber-optic cables, high-frequency radio waves called microwave signals were used to relay long-distance telecommunications

Wireless § Wireless networks, or Wi-Fi, use radio signals to connect computers. § Bluetooth technology is a wireless technology that works over short distances. § Infrared signals are light waves that cannot be seen by the human eye.

Using Modems § A modem makes it possible for your computer and telephone lines or TV cables to communicate. § The word modem names the work the device does: modulation and demodulation. Through modulation, the modem changes the digital signal of the computer to the analog sounds used by telephones.

Modem Speed § Modem speed is measured in bits per second, or bps, which is the amount of data that can be sent in one second. § Dial-up modems have been surpassed by newer, speedier technologies.

Sending Faxes § One machine still uses telephone lines to send printed messages or visual images. A facsimile machine, or fax machine, is a device that allows you to send pages of information to a fax machine anywhere in the world.

Bandwidth and Broadband § Bandwidth is the amount of data that can be sent through a modem or network connection. The more bandwidth, the faster the connection. § Broadband is the general term for all high-speed digital connections that transmit at least 1. 5 megabits per second (Mbps), though current broadband services transmit between 10 and 30 Mbps.

Broadband Transmission § You can use the Internet to send and receive messages over the telephone. § Voice over Internet Protocol (Vo. IP) technology allows you to have a telephone connection over the Internet.

Chapter Review § A modem translates digital and analog signals to allow phones and computers to communicate with one another. § Sending any kind of information over telephone lines is an example of telecommunications.

Chapter Review (continued) § You can use a fax machine to transmit any type of printed document; with e-mail, the printed document must be converted to digital format before it can be transmitted as an e-mail attachment. § It might be important for a home-office computer to have Internet service that offers a lot of bandwidth for a fast connection, quick downloads, and the ability to handle large volumes of data.