What device modulates signals to encode digital information and demodulates signals to decode the transmitted information?

What device modulates signals to encode digital information and demodulates signals to decode the transmitted information?

• A. Router
• B. Switch
• C. Bridge
• D. Modem

Answer: (D)

Modulation and demodulation of signals to carry digital information over a transmission medium is what a modem does. It converts digital data from a computer into an analog signal suitable for transmission over a physical medium like telephone lines, and at the receiving end, converts that analog signal back into digital data. The other devices have different roles: a router directs data between networks, a switch connects devices within a local network by forwarding frames, and a bridge forwards frames between network segments. None of these inherently perform modulation/demodulation for long-distance digital transmission.

Modulation and demodulation of signals to carry digital information over a transmission medium is what a modem does. It converts digital data from a computer into an analog signal suitable for transmission over a physical medium like telephone lines, and at the receiving end, converts that analog signal back into digital data. The other devices have different roles: a router directs data between networks, a switch connects devices within a local network by forwarding frames, and a bridge forwards frames between network segments. None of these inherently perform modulation/demodulation for long-distance digital transmission.