Coaxial cable, recognition symbol; coaxial transmission path; radio-frequency cable -  One conductor with one outer-conductor connection and one shielded connection (triax).
The broken line - — - indicates where line connection to a symbol is made and is not part of the symbol.
If necessary for clarity, an outer-conductor connection shall be made to the symbol.
Derived from files: [1] and [2].
(in English) (1993)  315-1975 - IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters), IEEE, p. 44  DOI:  10.1109/IEEESTD.1993.93397. ISBN:  0738109479.
Michel Bakni