Which of the following describes the roles of devices in a WAN?

Which of the following describes the roles of devices in a WAN? (Choose three.)

A.
A CSU/DSU terminates a digital local loop.

B.
A modem terminates a digital local loop.

C.
A CSU/DSU terminates an analog local loop.

D.
A modem terminates an analog local loop.

E.
A router is commonly considered a DTE device.

F.
A router is commonly considered a DCE device.

Explanation:
The idea behind a WAN is to be able to connect two DTE networks together through a DCE
network. The network’s DCE device (includes CSU/DSU) provides clocking to the DTE-connected
interface (the router’s serial interface).

A modem modulates outgoing digital signals from a computer or other digital device to analog
signals for a conventional copper twisted pair telephone line and demodulates the incoming
analog signal and converts it to a digital signal for the digital device. A CSU/DSU is used between
two digital lines -For more explanation of answer D, in telephony the local loop(also referred to as a subscriber
line) is the physical link or circuit that connects from the demarcation point of the customer
premises to the edge of the carrier or telecommunications service provider’s network. Therefore a
modem terminates an analog local loop is correct.