IEC 61643-22:2015 describes the principles for the selection, operation, location and coordination of SPDs connected to telecommunication and signalling networks with nominal system voltages up to 1 000 V r.m.s. a.c. and 1 500 V d.c. This standard also addresses SPDs that incorporate protection for signalling lines and power lines in the same enclosure (so called multiservice SPDs). This second edition cancels and replaces the first edition published in 2004. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - Update the use of multiservice SPDs (Article 8); - Comparison between SPD classification of IEC 61643-11 and IEC 61643-21 (7.3.3); - Consideration of new transmission systems as PoE (Annex F); - EMC requirements of SPDs (Annex G); - Maintenance cycles of SPDs (Annex I). Keywords: SPD, surge protective devices