What function does a modem perform in signal transmission?

A modem, short for modulator-demodulator, performs the essential function of converting digital signals from a computer into analog signals suitable for transmission over traditional phone lines, and vice versa. Specifically, it modulates the digital data into an analog format for sending, and then demodulates incoming analog signals back into digital data for the receiving device.

The correct answer highlights that a modem converts digital signals into two distinct analog frequencies, which aligns with its primary operation. This frequency modulation is crucial because it enables data to be transmitted effectively across mediums that primarily handle analog signals, such as telephone lines.

In addition, modems do not primarily focus on amplifying digital signals for clarity or directly reducing signal interference; their main function revolves around the modulation and demodulation process. While some modems may incorporate features related to signal quality, their fundamental role in the transmission process is more related to the conversion of signal types rather than amplification or interference reduction.