This is a photo of the fog horn's warning Sign, at St. Ann's Head Lighthouse. The lighthouse is intended to guide ships around a number of rocky shoals that cause a hazard to shipping entering the Haven as well as Crow's rock. The current lighthouse was completed in 1841 (at which time it was known as "St. Ann's Low Light") and commissioned by John Knott, senior lighthouse keeper with Trinity House. The first lighthouse on this site was built in 1714. The present operational tower is 13 metres in height (42.7 feet) and is painted white.St. Ann's Head Lighthouse is a lighthouse that overlooks the entrance to the Milford Haven waterway, one of Britain's deep water harbours, from St. Ann's Head near Dales in West Wales.
The blockhouse which is the control tower carries the fog horn. The device for activating the foghorn is a pair of electronic eyes placed opposite one another: when they can't see each other a signal whizzes off to Harwich and the foghorn is activated automatically.