What does ISDN stand for?

ISDN stands for Integrated Services Digital Network. This term refers to a set of communication standards that allow for the simultaneous transmission of voice, video, data, and other services over the traditional circuits of the public switched telephone network.

The "Integrated" aspect emphasizes that it supports multiple types of services, including both voice and data, which was a significant advancement over previous technologies that mainly focused on either voice or data transmission. "Services" relates to the various types of communications that can be handled, while "Digital Network" highlights that it operates over digital rather than analog signals, ensuring better quality and efficiency.

The other options incorrectly convey the meaning or purpose of ISDN. For instance, "Integrated Standard Data Network" and "Internet Standard Digital Network" do not accurately represent the nature of ISDN as a communication framework that integrates various forms of services. "International Services Digital Network" suggests a focus on international aspects, which does not capture the broader functionality of ISDN's integration of diverse services over digital connections.

Thus, the correct choice accurately reflects the comprehensive and multifaceted capabilities of ISDN.