What is the primary benefit of Asymmetric Digital Subscriber Line (ADSL)?

The primary benefit of Asymmetric Digital Subscriber Line (ADSL) is that it allows simultaneous voice and data transmission. This technology enables users to make phone calls while using the internet without interruption, which is particularly advantageous for residential users and businesses. ADSL achieves this by splitting the telephone line into different channels, one for voice communication and another for data transmission. The asymmetrical nature of ADSL means that the download speeds are typically much higher than upload speeds, catering to the common usage patterns where users download more information than they upload, such as streaming or browsing.

This capability is fundamental in scenarios where maintaining voice communication is necessary while accessing online services, thus enhancing the overall functionality and utility of traditional telephone lines. In contrast, other options do not relate to the defining features of ADSL technology. For example, boosting mobile network coverage pertains to wireless technology rather than fixed-line services like ADSL. Similarly, increasing ATM transaction speeds and acting as a universal payment processing system do not connect with the core functionality of ADSL.