Editing Digital selective calling (section)

==Technical details==
The DSC is a  synchronous system using characters composed from a ten-bit [[error detecting code]].  The bits are encoded using [[frequency-shift keying]].  For High Frequency and Medium Frequency two tones 170&nbsp;Hz apart either side of the allocated frequency with 100 [[Baud]] [[symbol rate]] are used. For VHF the two tones used are 1300 and 2100&nbsp;Hz with  a symbol rate of 1200 [[Baud]]. Each character is transmitted twice with a time delay.  The detailed specification is published in the [[International Telecommunication Union]] recommendation ITU-R M.493, revision 15 published in 2019 being the most recent.<ref name="itu-m493">{{cite web | publisher = [[International Telecommunication Union]] | title = M.493 : Digital selective-calling system for use in the maritime mobile service | year = 2019 | url = https://www.itu.int/rec/R-REC-M.493 }}</ref>