Symbol 5038 from IEC 60417 - Title/Meaning: Bass control Function/description: To identify the control for the lower audio frequencies.
Additional information: 
Published in: First edition, 1973
Own work using: iso.org/obp/graphics/grs/47b02cdd-5d41-4b70-a2a5-5985fcccf670 200.png
Vectorization:  Mrmw