How can I enter special response spectra?

As a consequence of the progressive microzonation of certain zones, it is increasingly necessary to work with special spectra that cannot be adapted to the standard parameterized spectra.

Such spectra are often presented in the form of curves or sets of curves, or a set of the parameters S, TB, TC, TD is specified. The program supports both types of input, which are described in chapter C 2.3 (generations 9 and 8) or C 4.2 (generation 7) of the manual..