What is used to connect a computer to a telephone line for dial up Internet?

The first two are system software and the third is application software. Examples of application software for communications: e-mail, FTP, Web browser, newsgroup/message boards, chat rooms, instant messaging, video conferencing, and VoIP.

Some communications devices are preprogrammed to accomplish communications tasks. Other communications devices require separate communications software to ensure proper transmission of data. Communications software works with the network standards and protocols defined earlier to ensure data moves correctly through a network. Communications software usually is bundled with the operating system or purchased network devices.

Often, a computer has various types of communications software, each serving a different purpose. One type of communications software helps users establish a connection to the Internet using wizards, dialog boxes, and other on-screen messages. Communications software also allows home and small office users to configure wired and wireless networks and connect devices to an existing network. 

COMMUNICATIONS OVER THE TELEPHONE NETWORK

The public switched telephone network (PSTN) is the worldwide telephone system that handles voice-oriented telephone calls (Figure 8-15). Nearly the entire telephone network today uses digital technology, with the exception of the final link from the local telephone company to a home, which often is analog.

The telephone network is an integral part of computer communications. Data, instructions, and information are transmitted over the telephone network using dial-up lines or dedicated lines. The following sections discuss dial-up lines and the various types of dedicated lines that use the telephone network for data communications.

Dial-Up Lines

A dial-up line is a temporary connection that uses one or more analog telephone lines for communications. A dial-up connection is not permanent. Using a dial-up line to transmit data is similar to using the telephone to make a call. A modem at the sending end dials the telephone number of a modem at the receiving end. When the modem at the receiving end answers the call, a connection is established and data can be transmitted. When either modem hangs up, the communications end.

Using a dial-up line to connect computers costs no more than making a regular telephone call. Computers at any two locations establish an Internet or network connection using modems and the telephone network.

Dedicated Lines

A dedicated line is a type of always-on connection that is established between two communications devices (unlike a dial-up line where the connection is reestablished each time it is used). The quality and consistency of the connection on a dedicated line are better than a dial-up line because dedicated lines provide a constant connection.

Businesses often use dedicated lines to connect geographically distant offices. Dedicated lines can be either analog or digital. Digital lines increasingly are connecting home and business users to networks around the globe because they transmit data and information at faster rates than analog lines.

Five types of digital dedicated lines are ISDN lines, DSL, FTTP, T-carrier lines, and ATM. Although cable television (CATV) lines and fixed wireless are not a type of standard telephone line, they are very popular ways for the home user to connect to the Internet. Fixed wireless Internet connections use an antenna on your house or business to communicate with a tower location via radio signals. Later sections in this chapter discuss the use of CATV lines and radio signals to connect to the Internet.

The table in Figure 8-16 lists the approximate monthly costs of various types of Internet connections and transfer rates (speeds), as compared with dial-up lines. The following sections discuss ISDN lines, DSL, FTTP, T-carrier lines, and ATM. 

ISDN LINES For the small business and home user, an ISDN line provides faster transfer rates than dial-up telephone lines. Not as widely used today as in the past, ISDN (Integrated Services Digital Network) is a set of standards for digital transmission of data over standard copper telephone lines. ISDN requires that both ends of the connection have an ISDN modem. The ISDN modem at your loca- tion must be within about 3.5 miles of the telephone company’s ISDN modem. Thus, ISDN may not be an option for rural residents.

DSL DSL is a popular digital line alternative for the small business or home user. DSL (Digital Subscriber Line) transmits at fast speeds on existing standard copper telephone wiring. Some DSL installa- tions include a dial tone, providing users with both voice and data communications.

To connect to DSL, a customer must have a special network card and a DSL modem. Not all areas offer DSL service because the local telephone company or the lines in the area may not be capable of supporting DSL technology. As with ISDN, DSL may not be an option for rural residents because the user’s location (and DSL modem) and the telephone company’s DSL modem must be located within about 3.5 miles of each other.

ADSL is one of the more popular types of DSLs. ADSL (asymmetric digital subscriber line) is a type of DSL that supports faster transfer rates when receiving data (the downstream rate) than when sending data (the upstream rate). ADSL is ideal for Internet access because most users download more information from the Internet than they upload.

FTTP FTTP, which stands for Fiber to the Premises, uses fiber-optic cable to provide extremely high-speed Internet access to a user's physical permanent location. Two specific types of FTTP are FTTH (Fiber to the Home) and FTTB (Fiber to the Building). With FTTP service, an optical terminal at your premises receives the signals and transfers them to a router connected to your computer. As the cost of installing fiber decreases, increasingly more homes and businesses will opt for this high-speed Internet access.

T-CARRIER LINES A T-carrier line is any of several types of long-distance digital telephone lines that carry multiple signals over a single communications line. T-carrier lines provide very fast data transfer rates. Only medium to large companies usually can afford the investment in T-carrier lines because these lines are so expensive.

The most popular T-carrier line is the T1 line. Businesses often use T1 lines to connect to the Internet. Many Internet access providers use T1 lines to connect to the Internet backbone. Home and small business users purchase fractional T1, in which they share a connection to the T1 line with other users. Fractional T1 is slower than a dedicated T1 line, but it also is less expensive.

A T3 line is equal in speed to 28 T1 lines. T3 lines are quite expensive. Main users of T3 lines include large companies, telephone companies, and Internet access providers connecting to the Internet backbone. The Internet backbone itself also uses T3 lines.

ATM ATM (Asynchronous Transfer Mode) is a service that carries voice, data, video, and multimedia at extremely high speeds. Telephone networks, the Internet, and other networks with large amounts of traffic use ATM. Some experts predict that ATM eventually will become the Internet standard for data transmission, replacing T3 lines. 

What is used to connect a dial

What is the Internet connection using telephone lines?