There are 3 key elements to the Dual Level Switch:
The switch is contained in a protective plastic body, and measure approximately 110 mm overall height and 60 mm diameter.
The Mounting Bracket
The Switch is secured on a mounting bracket. The Bracket can be secured either horizontally or vertically by 4 screws or bolts.
This picture shows the Switch and the Bracket separately:
Once the Bracket is fixed in position, the Switch is screwed into the Bracket.
The High and Low Levels are set by 2 "Sinkers", which are secured to the Switch by a Polyester Cord. This picture shows the 2 Sinkers held in position below the Switch:
The High and Low Level is set by adjusting the position of each Sinker.
This provides a very very robust system that is simple to install and which requires little, if any, maintenance.