Symbol 2811 from ISO 7000 - Title/Meaning: Slow operation Function/description: To indicate the slow setting of a function or mechanism; to identify the switch or switch position by which the rate of operation is decreased or set to its slow position.
pay attention to orientation of symbolAdditional information: 
The slow setting may be a distinct control (for example, a separate button) or a position to which a control is moved (for example, one side of a rocker control or one end of the motion of a lever control).
Own work using: iso.org/obp/graphics/grs/bf3382bc-3cea-4db4-bef3-725e530ec121 200.png
Vectorization:  Mrmw