The code consists of two parts: the self-consistent solution of the balance equations for all level populations and energy densities at all radial points and the computation of the emergent line profiles observed from a telescope with finite beam width and arbitrary offset.
All numerical discretizations are done in an adaptive way, the user has full error control and the line profiles may be computed in almost arbitrary accuracy. An accelerated lambda iteration is used to solve the equation system. The optical depths in the lines may vary between 0 and about 1000. The input of physical cloud parameters, telescope parameters, and numerical control parameters may be done either interactively or as file input.