Fourfold. Designating or of a former system of telegraphy in which four messages could be sent simultaneously over one wire, two in either direction.

How do you spell quadruplex?

fourfold; quadruple. noting or pertaining to a system of telegraphy by which four messages may be transmitted simultaneously over one wire or communications channel.

How many is quadruplex?

A quadruplex apartment is a residential unit with 4 private units that can each accommodate a separate individual or family.