Fog signal discontinued 14:15 hours 12th. August 2005
Thick mist or cloud of minute water droplets suspended in atmosphere at or near earth's surface
|Visibility Sensor VF-500-110T|
Replaced Visibilty Detector September 2003
An infrared beam is emitted and foward scatter is measured.
When visibility drops below 2 1/2 miles for more then six minutes the fog signal is operated and when visibilty is 2 1/2+ miles for more than six minutes the fog signal is switched off.
AGA ELG 300 Emitters.
A coil fed with AC current at 150 Hz.vibrates steel diaphragms to give a 300 Hz.tone.
Two emitters units mounted one above the other,give a nominal range of 4 miles
Showing Visibility Sensor from ground.
Control panels contain equipment to convert 240 Volt AC at 50 Hz.to 150 Hz.
The AC is converted to DC and fed to a transformer where two high current thyristers switch to give a square wave output.This is then taken through a variable transformer to adjust the output level and through a series of power factor correction capacitors to give the optium sound.
Emitter Diaphram 6mm thick
Operation of Fog detector and Fog signal is monitored at NLB's monitoring center.
Technicians visit at least annually to check,modify and update equipment as required.
Northern Lighthouse Board are gradually phasing out Fog Signals the remaining ones due to be discontinued in August 2005
Calf of Man used the Visibility Sensor VF-500-110T operation was similar to Point of Ayre
Point of Ayre fog signal discontinued 13:15hrs 17th August 2005
Last fog signal Skerryvore discontinued 4th.October 2005
All photographs Copyright Fred Fox..