A PF Cell, or Position Finding Cell to give it its full name, was used to find the position of a target vessel. They were invented in the 1870s and rapidly found a place in the coast artillery network of the Royal Artillery. Most coast batteries had two or more of these Cells. Using several meant that an accurate position of an enemy vessel could be found (right).
The bearing to the target from each Cell and the Depression Range Finder were plotted and the intersection of the plots gave a good position of the target. Armed with this information a coast artillery battery was better able to engage an enemy vessel.
There were at one time seven PF Cells on Mount Serapong alone. Three more were on Mount Imbiah, and another was at Fort Siloso beside the Battery Observation Post. At least one remains on Singapore Island, near the Labrador Battery.Often these were referred to as bunkers, which is incorrect. A bunker is something else completely.
A PF CEll near the Labrador Battery
ABOVE LEFT & CENTRE: A PF Cell which once stood near the Scripture Union Camp on Sentosa.
ABOVE RIGHT: A PF Cell at the Water Catchment area on Mount Serapong. This was the Serapong No.1 Cell.
ABOVE: Three views of a PF Cell on the slopes of Mount Serapong. This was the Serapong No.2 Cell.
ABOVE: The PF Cell behind the Serapong Spur Emplacement. This was the Serapong No.7 Cell.