8. Technical and economic considerations

8.1 Hardware modularity

On the first day of installation of a switching system at a given site, the number of user lines and circuits connected varies greatly from one site to another. Initial installation capacities may be very low, for example a few hundred users. Over time, extensions will be made and the system may reach its maximum capacity, which is usually several tens of thousands.

Operator revenues depend directly on the number of users connected. It is therefore normal for the operator's investment to be as linear a function as possible of the number of user lines (figure 48 ). But this curve of costs versus number of lines does not pass through zero,...