Symbol 5431 from IEC 60417 - Title/Meaning: Direct link Function/description: To indicate a channel which is accessible at the ends of a link but not at relay stations.
Additional information: 
Published in: Supplement K, 1991
Own work using: iso.org/obp/graphics/grs/3e8fc17e-86f8-47d7-b359-22f79d0659e3 200.png
Vectorization:  Mrmw