LOCAL AND LONG-DISTANCE NETWORKS
A fiber-optic or wire-pair cable bus feeds several RSUs.
A fiber-optic cable self-healing ring feeds RSUs.
Further breakdown among types of business subscribers as a function of white-collar
and blue-collar workers. For example, a large insurance company will have much
greater calling activity than a steel mill with the same number of workers.
It follows that in regions of high subscriber density typical of urban areas, there would be
many exchanges, each with comparatively short subscriber loops. Such a network would
trend toward mesh connectivities. The opposite would be in rural regions where we
would expect few exchanges, and a trend toward a greater use of tandem working. Long
172 LOCAL AND LONG-DISTANCE NETWORKS Figure 8.2d A fiber-optic or wire-pair cable bus feeds several RSUs.