In reply to David Barnard (Oxford Mail, October 11), the meaning of CQD is not Come Quickly Do - it is Come Quickly Distress.

A strict interpretation would be 'All Stations, Distress'.

Marconi suggested that CQD be the recognised distress signal in 1904.

SOS was introduced after much deliberation at the second Berlin Radiotelegraphic Conference in 1906.

The thinking was that three dots, three dashes and three dots could not be misinterpreted.

SOS was internationally recognised in 1908, but the vast majority of British vessels, including the ill-fated Titanic, continued to use CQD.

The United States did not officially adopt SOS until 1912, being slow to adopt international wireless standards.

NC NEWMAN Severn Crescent Cavendish Park Didcot