This is used on a pneumatic schematic to show that branch lines split off the main line.

In pneumatic schematics, a dot is employed to indicate the junction where branch lines diverge from the main line. This specific symbol serves to clearly mark connection points in the system, allowing for an easy understanding of how compressed air flows through a network of pipes. When technicians or engineers analyze these schematics, the presence of a dot reveals that multiple pathways branch from a single main line, facilitating both the design and troubleshooting processes in pneumatic systems.

The other symbols in the options serve different functions. Circles may signify points of connection or termination, triangles can denote flow direction or specific actions, and arrows typically indicate the direction of air flow or movement within the system. Thus, choosing a dot as the correct answer effectively highlights its unique role in illustrating branching connections in pneumatic schematics.