Explanation:
When we reverse the directions of all branch transmittances and interchange the input and output in the flow graph, the resulting structure is called as Transposed Form. Let's understand this in detail.

Transposed Form:

- The transposed form of a linear system is another way of representing the same system.
- In the transposed form, the direction of all branch transmittances is reversed, and the input and output are interchanged.
- The transposed form is obtained by replacing every node with an associated branch and vice versa.
- In the transposed form, the output is now the input, and the input is now the output.
- The transposed form maintains the same transfer function as the original system.

Direct Form-I:

- The direct form-I is a structure that represents a linear system as a sum of products of its coefficients and delayed input samples.
- The direct form-I is obtained by using the coefficients of the transfer function to form a set of feedforward paths.
- The feedback paths are formed by delaying the output and multiplying it with the feedback coefficients.
- The direct form-I has a feedforward structure that is followed by a feedback structure.

Direct Form-II:

- The direct form-II is another structure that represents a linear system as a sum of products of its coefficients and delayed input samples.
- The direct form-II is obtained by using the coefficients of the transfer function to form a set of feedback paths.
- The feedforward paths are formed by delaying the input and multiplying it with the feedforward coefficients.
- The direct form-II has a feedback structure that is followed by a feedforward structure.

Conclusion:

In summary, when we reverse the directions of all branch transmittances and interchange the input and output in the flow graph, the resulting structure is called as Transposed Form. This is different from Direct Form-I and Direct Form-II, which are structures that represent a linear system as a sum of products of its coefficients and delayed input samples.