This guide applies to surge protectors used in balanced or unbalanced data, communication and signaling circuits with voltages equal to or less than 1000Vrms or 1200 Vdc. The surge protectors covered are multiple-component series or parallel combinations of linear or non-linear elements, packaged for the purpose of limiting voltage, current, or both. This guide is intended to complement the IEEE Std C62.36-2000. The definitions used in the Application Guide and the Test Methods Standard are the same. For other terms not defined in the Guide or the Standard, see IEEE Std 100-1996. This guide is not intended to apply to packaged single-component gas tube or air gap arresters, which are covered by IEEE C62.42. The purpose of this guide is to enable the reader to understand the function and performance tests of the various types of multiple-component data, communication and signaling circuit protectors in terms of particular applications. Consideration is given to the characteristics of multiple-component protectors and the concepts necessary to choose the appropriate product and interpret its specifications.