This section of IEC 839-5 specifies the general requirements for the performance, reliability and security characteristics of alarm transmission systems. It covers the general requirements for connections providing signalling between an alarm system and an alarm receiving centre. Additional requirements for specific alarm transmission systems are given in separate sections as parts of IEC 839-5. This does not preclude the use of any transmission system not - covered by one of these specific sections, provided that it meets these general requirements. This section does not specify the method of display of information and the installation of equipment.