History-Telephone system

• In the telephone system, it would be too expensive to use wires running between telephone exchanges to carry only one conversation.
• From early on, communications engineers have been looking for ways to increase the number of simultaneous connections carried over a single copper pair.
• FDMA was first used in 1918 by ``Ma Bell'' to carry four simultaneous conversations per wire between Pittsburgh and Baltimore.
• TDMA is applicable to digital transmissions only and was first introduced in the '60s.
• Today, coaxial cables can carry tens of thousands of simultaneous conversations simultaneously.

To probe further:

1.

Pierre Catala, FDM Hierarchy, in The Communications Handbook, J. Gibson, Ed., p. 301-307.

2.

B.P. Lahti and M.A. Wright, Digital Hierarchy,in The Communications Handbook, J. Gibson, Ed., p. 377-385.