Definition:  ratio of the complex quantity representing a timevarying quantity in terms of complex frequency at the output of a linear timeinvariant twoport, to the complex quantity representing the corresponding input quantity, the two complex quantities being defined in the same manner
NOTE – The complex quantities are generally the Laplace transforms of the timevarying quantities. In this case, the transfer function is the Laplace transform of the impulse response, and the term "fonction de transfert isomorphe" is used in French.
