What is the primary function of an Intermediate Distribution Frame (IDF)?

The primary function of an Intermediate Distribution Frame (IDF) is to distribute services within a building. IDFs serve as a termination point for various cables and are typically located on each floor or in different areas of a building, allowing for efficient management of telecommunication and data distribution. This function is crucial in a structured cabling system because it facilitates the connection of individual end-user devices to the backbone infrastructure, thus ensuring that network services can be delivered effectively throughout the facility.

When considering the other options, while backbone cables are indeed involved within a larger network infrastructure, the primary purpose of an IDF is not just to connect these cables, but to provide service distribution to the users. Terminating external cables is mainly performed at the Main Distribution Frame (MDF), which handles incoming connections from external service providers. Signal amplification usually occurs in specific network components such as amplifiers or repeaters but is not a direct function of the IDF. Thus, the role of the IDF is distinctly focused on managing internal service distribution, making option B the most appropriate choice.