The telegraph-telephone frequency-division multiplex transmission engineers

Just as the growth of telegraph traffic and the pressure of economic factors led the early telegraph engineers to develop duplex and quadruplex telegraph systems capable of transmitting two or four messages simultaneously on a single wire, so the growth of intercity telephone communication created demands for providing ever more telephone channels on a pair of wires or a single coaxial cable. This was paralleled by the need similarly to provide more than just two or four telegraph channels on a single transmission path.