Modem function for connectivity – UGC NET Question

A modem performs the dual processes of modulation and demodulation to enable digital devices to communicate over analog channels. It converts digital bits into analog waveforms suitable for traditional telephone lines and then reconverts received analog signals back into digital form. This functionality historically allowed computers to access the Internet via dial-up and continues in various broadband forms. Therefore the device described is a modem.

Option A:
Option A, router, forwards packets between networks based on IP addresses but assumes digital signals on both sides. It does not inherently change signals from digital to analog or vice versa.

Option B:
Option B, switch, operates within a local area network to direct Ethernet frames between devices and does not interface with analog telephone lines. Its function is packet switching rather than modulation.

Option C:
Option C is correct because the very name modem arises from combining the words modulation and demodulation. Its purpose is to serve as a bridge between digital equipment and analog transmission media, exactly as described in the question.

Option D:
Option D, repeater, boosts or regenerates signals to extend the distance they can travel on a network. It does not change the fundamental signal type from digital to analog or back.