 requires N*(N-1)/2 links]. Clearly a directly connected network is not practical. Initially telephony switchboards were manually operated. A caller told the name, and later on the number, of a desired party to a switchboard operator (illustrated in Figure 3.4) who connected the parties and disconnected when the call ended. Switchboard operators were mainly young women, as it became clear that they could concentrate and remember subscriber details better than men. Female operators however usually lost their jobs when they married, as marriage was considered a distraction and a valid reason for dismissal. This resulted in a rather limited workforce size. Furthermore, training costs and sal- aries in general meant that switching was a major operational cost. These motivated development of automatic switching in the early 20th century. Indeed, a number of early telephone operators relied on automatic switching as a competitive advantage vis-à-vis the BTC [1]. With the growth of subscriber numbers it became necessary to use multiple switches in a hierarchical configuration, as shown in Figure 3.5, to reduce the cost of wiring. While each subscriber still had a dedicated connection, the length of connection to the switch could be significantly reduced. Furthermore, hierarchical switching also allowed for a larger number of Broadband Telecommunications Technologies and Management Figure 3.4 Photograph of women working at a Bell system telephone switchboard and an early switch- board. Source: Ref. [3] Figure 3.5 Hierarchical switching subscribers to be served as the capacity of a switchboard was limited. Due to the hierarchical switching configuration, long-distance connections needed to be set up through operators in advance. Automatic switching allowed for a faster and less expensive call set up. Nowadays, a typical telephone call goes through a number of automatic exchanges, which switch the call to its destination, as shown in Figure 3.6. The connection between a customer's premise and the local exchange has remaine