Which of the following transmission directions listed is not a legitimate channel?

Which of the following transmission directions listed is not a legitimate channel from the following options below

A) Simplex

B) Half Duplex

C) Full Duplex

D) Double Duplex

Legitimate channel is opposite of Covert channel

In simplex transmission mode, the communication between sender and receiver occurs in only one direction. The sender can only send the data, and the receiver can only receive the data. The receiver cannot reply to the sender.

Double Duplex

Modes of Transmission Simplex vs Duplex vs Full Duplex

Simplex	Half duplex	Full duplex
Simplex in only one way communication.	Half duplex mode is a two-way communication but one mode is active at a time.	Full duplex mode is a two-way directional communication simultaneously.
In simplex mode, Sender can send the data but can’t receive the data.	In half duplex mode, Sender can send the data and also can receive the data but not simultaneously	In full duplex mode, Sender can send the data and also can receive the data simultaneously.
The simplex mode provides less performance than half duplex and full duplex.	The half duplex mode provides less performance than full duplex.	Full duplex provides better performance than simplex and half duplex mode.
Example :Keyboard and monitor.	Example : Walkie-Talkies.	Example : Telephone.

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