HL7 defines character sequences to represent ’special’ characters not otherwise permitted in HL7 messages. These sequences begin and end with the message’s Escape character (usually ‘\’), and contain an identifying character, followed by 0 or more characters. The most common use of HL7 escape sequences is to escape the HL7 defined delimiter characters.
| Character | Description Conversion |
|---|---|
| Cxxyy | Single-byte character set escape sequence with two hexadecimal values not converted |
| E | Escape character converted to escape character (e.g., ‘\’) |
| F | Field separator converted to field separator character (e.g., ‘|’) |
| H | Start highlighting not converted |
| Mxxyyzz | Multi-byte character set escape sequence with two or three hexadecimal values (zz is optional) not converted |
| N | Normal text (end highlighting) not converted |
| R | Repetition separator converted to repetition separator character (e.g., ‘~’) |
| S | Component separator converted to component separator character (e.g., ‘^’) |
| T | Subcomponent separator converted to subcomponent separator character (e.g., ‘&’) |
| Xdd… | Hexadecimal data (dd must be hexadecimal characters) converted to the characters identified by each pair of digits |
| Zdd… | Locally defined escape sequence not converted |
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