IEC 60839-5-1:2014 specifies the requirements for the performance, reliability, resilience and security of alarm transmission systems and ensures their suitability for use with different types of alarm systems and annunciation equipment. This standard specifies the requirements for alarm transmission systems providing alarm transmission between an alarm system at supervised premises and annunciation equipment at an alarm receiving centre. It applies to transmission systems for all types of alarm messages such as fire, intrusion, access control, social alarm, etc. This edition includes the following significant technical changes with respect to the previous edition published 24 years ago: techniques and constraints have been widely changed since that time, which has been reflected in this new edition.