adjective Of or relating to a system in telegraphy by which four messages (two in each direction) can be sent on one wire simultaneously.
adjective Of or relating to an early videotape format with four magnetic record/reproduce heads mounted on a headwheel spinning transversely across the tape.
noun A quadruplex system.
noun Clipping of quadruplex videotape, an early type of videotape with four magnetic record/reproduce heads mounted on a headwheel spinning transversely across the tape.