Triangles are standard for low voltage cable drops. You can also use a subscript number to identify unique cases like the paging and television drops and then put in a legend more specific like “for paging speakers to be mounted in ceiling tile” you can also number all the drops and then in a spreadsheet have more detail about each drop.
If you Google search something like “low voltage floor plans” or “electrical plans” I suspect you will find some good examples to reference.
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