An automatic collision warning system for use at sea, using present-day lower power techniques and capable of handling up to 250 ships at a time is described. The equipment does not involve expensive computer facilities.

During the past twenty years I have sailed my ketch Mara (12 tons) in the English Channel and have been involved in several close-quarter situations with large merchant ships, fortunately without accident. Any competent navigator is aware that if the bearing of the other vessel remains constant, there is a risk of collision. In Mara's case, moving at a fast walk, the threat on 090° coming at 20 kt. may pass ahead or astern. If the threat signals her intention by one or two blasts there is no problem; it is the ship that holds her course in blind silence that gives the yachtsman a cause for heart failure.