This paper analyses three models with overflow traffic and different serving intensities in primary and secondary trunk groups, which represent specific cases in circuit switching telecommunication networks . Explicit solutions for traffic parameters as well as the numerical iterative procedure to resolve steady state system equations are used in the analysis. For the complex model with two overflow traffic systems with changed serving intensity, we suggest a procedure to overcome the problems of resolving a system with a great number of steady state equations while keeping the advantages of an analytic solution compared to statistics modeling.