1. Pneumatic Signal Symbol: A pneumatic signal, which uses compressed air (typically 3-15 psi) to transmit information or move actuators, is represented by a solid line with double diagonal slashes ($//$ ) at regular intervals.
2. Other Common Signal Symbols:
• Electric Signal: Represented by a dashed line ( --- --- --- ) or a solid line with three slashes ($///$ ).
• Hydraulic Signal: Represented by a line with 'L' shapes or specific patterns of slashes and circles.
• Capillary Tubing: Represented by a line with 'X' marks.
• Software/Data Link: Often represented by a line with circles or bubbles.
3. Importance of Standardization: Using these specific line types allows engineers and technicians from anywhere in the world to look at a diagram and immediately know whether a control valve is being moved by electricity, air, or hydraulic fluid.