Symbol 5500 from IEC 60417 - Title/Meaning: Three-party call Function/description: To identify the control which allows a telephone conference between this telephone and two other parties.
Additional information: 
See ITU-T Recommendation E.121
Published in: Supplement J, 1990
Own work using: iso.org/obp/graphics/grs/ad042950-daba-44ae-bc90-ed4de96f75d7 200.png
Vectorization:  Mrmw