This part of IEC 62297 specifies how the trigger messages defined in IEC 62297-1 are transmitted. A trigger is defined as information sent from a service provider as part of a data broadcasting transmission that initiates an application in a receiver. Additional information in the trigger message allows filtering or prioritization techniques to be applied at the receiver. Examples of possible use include the forcing of the display of information to warn of severe weather conditions and advising of extreme content in the TV programme. In an interactive system, a message or icon might be displayed inviting on-line access to vote, to register an interest in an advertised product, or to browse programme-related content. This standard specifies how trigger messages are broadcast using teletext technology. Both Page Format-Clear and Independent Data Line methods are defined, using protocols defined in ETSI EN 300 708.