We present the replacement and modification of the Debye temperature θD by the average phonon frequency in the Rowell [Solid State Commun. 19 (1976) 1131] linear transition-temperature equation for superconducting materials. We not only improve Rowells results but also describe the experimental results accurately and consistently for the various superconducting systems which cover the entire range of λ between 0.72 and 2.59. The proposed linear equation of the transition temperature Tc is found to be better and more accurate than those of Jain and Kachhava [Can. J. Phys. 58 (1980) 1614].