Abstract <p>For a mathematical model of the electromagnetic induction in a coaxial cable line by a radiation pulse, based on a telegraphic approximation, the transformation of source functions through the density functionals of an external electric current in insulation is presented. The calculation results are compared with the results obtained using a three-dimensional program for calculating the internal electromagnetic pulse inside a coaxial cable line. The presented mathematical model makes it possible to calculate the parameters of electromagnetic induction in a coaxial cable line with significantly less machine time compared to a three-dimensional calculation program with almost no loss of accuracy. This is especially important when performing calculations in structurally difficult objects (a large number of internal communication lines, the presence of cable harnesses consisting of cables with different physical and technical characteristics).</p>