Quadruplex system

(Electric Telegraph) a system by which four messages, two in each direction, may be sent simultaneously over the wire.

See also: Quadruplex

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
Accordingly, applications in duplex, triplex or quadruplex systems are highly feasible.
The advantage of reduced size is most relevant when operating with multiple extruder systems, such as duplex, trip- or quadruplex systems. Figure 4 is a side view drawing of the extremely compact arrangement of three MCTD extruders around a triplex extrusion head.