Which of the following types of DSL allows simultaneous internet use and telephone calls?

Asymmetric DSL (ADSL) is the type of DSL that allows for simultaneous internet use and telephone calls. This is achieved through the use of frequency division multiplexing, which separates the data signals for internet and voice telephone calls over the same line. In ADSL, the bandwidth is allocated in such a way that it supports high-speed data transmission for internet use while still allowing the lower frequency range to be used for standard voice calls.

This capability is particularly advantageous for households and businesses since it enables users to make phone calls without interrupting their internet connection. The design of ADSL specifically accommodates asymmetric data rates, meaning it typically provides higher download speeds compared to upload speeds, suiting the needs of standard internet usage patterns.

Other options that do not provide this simultaneous functionality include dial-up, which requires a dedicated phone line and cannot handle voice calls while connected to the internet. Symmetric DSL (SDSL) offers equal upload and download speeds but also doesn’t support simultaneous phone calls like ADSL does. Cable connections, while capable of simultaneous internet and phone service, operate on a different technology (cable broadband) that is distinct from DSL. Thus, ADSL is the correct answer as it facilitates both services on the same line effectively.