Symbol 5211 from IEC 60417 - Title/Meaning: Listen Function/description: To indicate a ""listen"" facility.
Additional information: 
Published in: 3C/1016/FDIS, 3C/1046/RVD;2002-10-07
Own work using: iso.org/obp/graphics/grs/331e4751-0c44-45c7-92da-8454701353c7 200.png
Vectorization:  Mrmw