A SPICE model is proposed to simulate a typical box-to-box structure when the interconnect is a two-wire shielded cable. The goal is to carry out a very simple circuit that can be easily implemented by any user interested in investigating conducted transient immunity of a parallel-pair (twinax) or twisted-pair shielded cable. The model is based on the classic cable representation as a cascade of lumped element circuit cells obtained considering the cable as a three-conductor transmission line (TL) above a reference plane. Particular attention is here addressed to properly define the mutual inductive coupling between the wires and the shield in order to take into account the penetration through apertures proper of real braided shields. The model is suitable for direct transient analysis and allows modeling any kind of cable terminations.