Trigger - (On-screen Trigger, Triggers, ATVEF Triggers, Red Key Trigger) - This was originally coined by the ATVEF and refers to something in the display that makes the viewer aware of the availability of optional interactive TV. A trigger can be presented in various forms including text and icons.
ATVEF interactive TV triggers were typically inserted into the vertical blanking interval of analog TV signals, (line 21 of the NTSC signal) the same place where closed-captioning data was inserted.
In the UK the phrase Red Key Trigger describes a prompt on the TV display that invites users to press the red button on their remote control device to initiate interactivity.
See TV Crossover Links