IEC 60870-5-101:2003+A1:2015 Applies to telecontrol equipment and systems with coded bit serial data transmission for monitoring and controlling geographically widespread processes. Defines a telecontrol companion standard that enables interoperability among compatible telecontrol equipment. The defined telecontrol companion standard utilizes standards of the IEC 60870-5 series of documents.This publication is of high relevance for Smart Grid. This consolidated version consists of the second edition (2003) and its amendment 1 (2015). Therefore, no need to order amendment in addition to this publication.