When we are given a desired CT system that we wish to implement is. If Hc(jΩ) is band-limited (BL), Heff(jΩ)=Hc(jΩ)=Hc(jω/T)=H(ejω) because of FT of Impulse Train is impulse train and h[n]=hc(nT) (definition)
that’s FT is H(ejω)=T1Hc(jω/T) so we need to multiply T