What device is used to modulate digital signals into analog signals for transmission?

The device that modulates digital signals into analog signals for transmission is a modem. A modem, short for modulator-demodulator, serves a critical role in communication systems by converting digital data from a computer or digital device into an analog signal that can be transmitted over traditional telephone lines, coaxial cables, or other media. This conversion is essential for enabling the communication of digital information over distances where analog transmission is the norm.

On the receiving end, the modem then demodulates the analog signal back into digital form so that it can be understood and processed by the receiving device. This two-way conversion allows for effective communication in various networking contexts, particularly in internet connectivity.

While routers, repeaters, and switches are important devices in networking, they serve different functions. Routers direct data traffic between different networks, repeaters amplify signals to extend transmission distances, and switches connect devices within the same network to facilitate communication. None of these devices perform the modulation function that is characteristic of a modem.