Dr. Campbell's Memoranda of 1907 and 1912

As mentioned in the preceding article by Dr. Jewett, the first and second of the three following memoranda were the basis of methods of designing transpositions for voice-frequency circuits. They applied particularly to non-loaded circuits but the theory was readily extended to cover loaded circuits. In an earlier and more general study written in 1904, Dr. Campbell considered the involved equations necessary to a n exact solution of the crosstalk problem and deduced simplifying approximations and convenient artifices for avoiding lengthy derivations.