I was reading a textbook which says:
Baseband transmission requires that we have a low-pass channel, a channel with a bandwidth that starts from zero. This is the case if we have a dedicated medium(such as coaxial or fiber optic cable) with a bandwidth constituting only one channel. For example, the entire bandwidth of a cable connecting two computers is one single channel.
I'm a little bit confused, if dedicated medium means low-pass channel, why we still need Broadband Transmission (Using Modulation) to have bandpass channel—a channel with a bandwidth that does not start from zero and we need to convert the digital signal to an analog signal before transmission. Because for example, broadband transmission using modulation is the sending of computer data througha telephone subscriber line, the line connecting a resident to the central telephone office.
Isn't the subscriber line also a dedicated medium, connecting a user and telephone office?