What type of technology is represented in the graphic that follows?

A.
Asynchronous Transfer Mode

B.
Synchronous Optical Networks

C.
Frequency-division multiplexing

D.
Multiplexing

Explanation:
D: Multiplexing is a method of combining multiple channels of data over a single transmission path. The transmission is so fast and efficient that the ends do not realize they
are sharing a line with many other entities. The systems “think” they have the line all to themselves. Telephone systems have been around for about 100 years, and they started
as copper-based analog systems. Central switching offices connected individual telephones manually (via human operators) at first, and later by using electronic switching
equipment. After two telephones were connected, they had an end-to-end connection, or an end-to-end circuit. Multiple phone calls were divided up and placed on the same
wire, which is multiplexing.
A is incorrect because Asynchronous Transfer Mode (ATM) is a high-speed network technology that is used in LAN and WAN implementations by carriers, ISPs, and
telephone companies. This technology is not what is shown in the graphic. ATM encapsulates data in fixed cells and can be used to deliver data over the Synchronous Optical
Networks (SONET) network. The analogy of a highway and cars is used to describe the SONET and ATM relationship. SONET is the highway that provides the foundation (or
network) for the carsthe ATM packetsto travel on.
B is incorrect because Synchronous Optical Networks (SONET) is actually a standard for telecommunications transmissions over fiber-optic cables. Carriers and telephone
companies have deployed SONET networks for North America, and if they follow the SONET standards properly, these various networks can communicate with little difficulty. A
metropolitan area network (MAN) is usually a backbone that connects LANs to each other and LANs to WANs, the Internet, and telecommunications and cable networks. A
majority of today’s MANs are SONET or FDDI rings provided by the telecommunications service providers.
C is incorrect because frequency-division multiplexing is a form of signal multiplexing that involves assigning nonoverlapping frequency ranges to different signals or to each
“user” of a medium. This is a type of multiplexing, but works over wireless signal spectrums instead of a time-based approach shown in the graphic. It can also be used to
combine multiple signals before final modulation onto a carrier signal. In this case the carrier signals are referred to as subcarriers; each frequency within the spectrum is used
as a channel to move data. An example is a stereo FM transmission.