Abstract :
The letter of Mr. V. J. Cissna in the November 1942 issue of Electrical Engineering, page 587, is of interest to the writer, who has also noted the difficulty commented upon and would like to make some suggestions. Mr. Cissna has really put three questions which will be dealt with separately. The first concerns the differing signs in the two pairs of general equations; the second concerns the interchanging of the A and D constants; and the third concerns the physical significance of these A and D constants.
