Quadruplex

"Quadruplex" is a technical term from the communications and recording industries and may refer to Quadruplex telegraphy, an improvement on the electrical telegraph patented in 1874 by Thomas Edison;
2 inch Quadruplex videotape, the first practical and commercially successful videotape format;
a shortened form for the four-stranded nucleic acid structure, more properly described as a G-quadruplex.

"Quadruplex" can also refer to a building split into four apartments, similar to a duplex.