What are some ways to accomplish full-duplex (FDX) digital communications on guided medium at the physical layer (OSI Layer 1)? a. Separate digital receive and transmit paths onto their own physical channels/circuits b. Modulate receive and transmit channels onto different carrier frequencies, thus allowing FDX on the same physical medium c. Separate transmit and receive channels on the same physical medium by separating them in time (i. e., TDM) d. All of the above

d. All of the above

Explanation:

Physical layer is the lowest layer of the OSI reference model that deals with the setup of physical connection to the network and with transmission and reception of signals.

Full duplex (FDx) is a bidirectional type of communication system where two end nodes send and receive data signals at the same time, and a single carrier is simultaneously used for dual communication.

To send or receive data, the participating nodes in a Full Duplex system do not have to wait for a free carrier/medium. It employs a medium that has at least two internal channels - one for sending and one for receiving.

Based on the above explanations, options A, B and C are valid and are correct ways to accomplish full-duplex (FDX) digital communications on guided medium at the physical layer (OSI Layer 1). There all of them are correct.