Final answer:
A DSL (Digital Subscriber Line) operates over telephone lines using a different frequency than that of telephone voice communications, allowing simultaneous internet access and phone usage.
Step-by-step explanation:
A device that operates over telephone lines but uses a different frequency than the telephone frequency is known as a DSL (Digital Subscriber Line). DSL technology allows for data transmission over telephone lines without interfering with voice service by using higher frequency bands. As a result, users can access the internet and make phone calls simultaneously. Unlike a dial-up modem, which uses the same frequency as telephone voice communications, DSL provides a higher bandwidth connection. On the other hand, cable modems use the coaxial or fiber optic cables provided by cable service providers, and fiber-optic modems employ laser signals along optical fibers for high-speed data transmission, usually not over telephone lines.