What type of telecommunication technology is illustrated in the graphic that follows?

A.
Digital Subscriber Line

B.
Integrated Services Digital Network

C.
BRI ISDN

D.
Cable modem

Explanation:
D: The cable television companies have been delivering television services to homes for years, and then they started delivering data transmission services for users who have
cable modems and want to connect to the Internet at high speeds. Cable modems provide high-speed access, up to 50 Mbps, to the Internet through existing cable coaxial and
fiber lines. The cable modem provides upstream and downstream conversions. Not all cable companies provide Internet access as a service, mainly because they have not
upgraded their infrastructure to move from a one-way network to a two-way network. Once this conversion takes place, data can come down from a central point (referred to as
the head) to a residential home and back up to the head and onto the Internet.
A is incorrect because Digital Subscriber Line (DSL) is another type of high-speed connection technology used to connect a home or business to the service provider’s central
office. It uses existing phone lines and provides a 24-hour connection to the Internet. This does indeed sound better than sliced bread, but only certain people can get this
service because you have to be within a 2.5-mile radius of the DSL service provider’s equipment. As the distance between a residence and the central office increases, the
transmission rates for DSL decrease. DSL does not go through the cable TV lines and does not have to go through the conversion from analog to digital and back as illustrated
in the graphic. DSL is a broadband technology that can provide up to a 52 Mbps transmission speed without replacing the carrier’s copper wire.
B is incorrect because the Integrated Services Digital Network (ISDN) is a communications protocol provided by telephone companies and ISPs that does not need to go
through the conversion process shown in the graphic. This protocol and the necessary equipment enable data, voice, and other types of traffic to travel over a medium in a digital
manner previously used only for analog voice transmission. Telephone companies went all digital many years ago, except for the local loops, which consist of the copper wires
that connect houses and businesses to their carrier provider’s central offices. These central offices contain the telephone company’s switching equipment, and it is here the
analog-to-digital transformation takes place.
C is incorrect because the Integrated Services Digital Network (ISDN) breaks the telephone line into different channels and transmits data in a digital form rather than the old
analog form. ISDN provides two basic home and business services: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). BRI has two B channels that enable data to be
transferred and one D channel that provides for call setup, connection management, error control, caller ID, and more. The bandwidth available with BRI is 144 Kbps, whereas
the top modems can provide only 56 Kbps. The BRI service is common for residential use, and the PRI, which has 23 B channels and one D channel, is more commonly used in
corporations.