The following principles have been adopted in respect of line-up and maintenance action limits for analogue and digital international circuits, links and lines: There should be separate limits for line-up and maintenance action. There should be a single limit specified for maintenance action, and this limit should be chosen such that, if exceeded, a fault would be considered to exist. (However, the subject of prompt and deferred maintenance action requirements is under study and the result of this study may reflect on the number of limits required for maintenance action.)