Why is constant bit rate (CBR) telephony classified as a circuit switching technology?

Constant bit rate (CBR) telephony is classified as a circuit switching technology primarily because it establishes a dedicated communication path or circuit between the caller and the receiver for the entire duration of the call. This means that a specific amount of bandwidth is reserved for this connection, ensuring a consistent and predictable data rate throughout the conversation.

Option B accurately describes this characteristic, emphasizing the involvement of customer-to-customer circuit switching which means that the call setup sequences create a fixed connection between users facilitated by headend equipment, maintaining that dedicated circuit until the call ends.

In contrast, the other options do not correctly define the principles of circuit switching. While packet switching techniques (mentioned in option A) are relevant to data transmission, they differ fundamentally from circuit switching as they do not establish a dedicated path and instead divide data into packets that share resources. Option C’s mention of fiber optic networks does not inherently relate to the classification of circuit switching and could apply to various transmission methods. Option D refers to mobile telephony applications, which can utilize both circuit and packet switching technologies, thus not specifically applicable to the characteristics of CBR telephony under discussion.