With the advent of quick fire guns and machine guns it was quickly realised that Defence Electric Lights were highly vulnerable to hostile fire. Various methods were adopted including:
- The provision of steel shutters to cover the projector.
- Attempts were also made to conceal lights in dead ground such as the fixed beams lights close to the shore line.
- Adoption of the ‘Port Hole’ lens which was fitted over the front of the projector to give a concentrated beam. This allowed the light to pass through a narrow opening in armour plate before opening out again into a wider beam.
- The see-saw searchlight and variations of this which allowed the projector to remain covered in a bunker, with the light projected from a mirror on a beam that could be moved up and down. See images below.