has an 8-character address. Order of transmission The order of transmission of messages on a given circuit is determined by their priority codes: Level 1 Messages with priority codes SS, QS, or QC. These are handled before all other messages. Level 2 Messages with priority codes QU or QX. These are handled before messages of levels 3 and 4. Level 3 Messages with a QK code, a Q code other than QS, QC, QU, QX, and QD, or no priority code. These are handled before messages of level 4. Note: Messages with a priority code which starts with any other letter than Q (with the exception of SS) are treated as having no priority code. Level 4 Messages with priority code QD. These are deferred until no messages of levels 1, 2, or 3 are waiting for transmission. However, level 4 messages are delivered not later than the morning following the day they were handed in for transmission. See also ACARS References Aviation communications Meteorological data and networks Telegraphy