Signals for warning against the presence German submarines according to the Dutch newspaper Algemeen Handelsblad dated 27 May 1915

An item reported that the secretary of the British Admiralty announced which signals could be used as warning for the possibility of German submarines in the neighbourhood. At daylight could the flag with the letter ‘B’ above a ball (International Code of Signals) be hoisted and by night continuous the letter ‘S’ using a flickering light.