CCNA Routing and Switching (legacy) — Question 80

What is the difference between a CSU/DSU and a modem?

Answer options

• A. A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line.
• B. A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line.
• C. A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line.
• D. A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line. D

Correct answer:

Explanation

The correct answer is D because a CSU/DSU is responsible for converting digital signals from a router to a leased line, which is typically used for dedicated connections. A modem, on the other hand, is designed to convert digital signals from a router to analog signals suitable for transmission over a phone line or similar medium. The other options incorrectly describe the functions of either device.