A data hold is to be constructed that reconstructs the sampled signal by the straight-line approximation shown

Question:

A data hold is to be constructed that reconstructs the sampled signal by the straight-line approximation shown in Fig. P3.7-9. Note that this device is a polygonal data hold with a delay of T seconds. Derive the transfer function for this data hold. Is this data hold physically realizable? 0 T Input to sampler Data-hold output 2T 3T 4T 1