Information Technology Reference
In-Depth Information
transferred through the central machine to the person you're call
ing. Assuming for the moment that your desired number designates
another telephone at your school, the central switch has the respon
sibility to pass information from your telephone to the one you have
dialed and also to pass information back. In modern telephone sys
tems, a central switch may make a temporary circuit between your
telephone and the one called, and communications then utilize that
circuit. Another approach would be for the central machine to re
ceive a communication from one telephone, store that information
centrally for a moment, and then forward it along to the desired re
ceiver. Although this storeandforward approach is not so common
within local telephone switches, variations of this idea are used in
various computer networks.
Star networks can work well (particularly for telephones) if the
number of telephones or computers is reasonably small, as in a busi
ness, school, or small town. To serve more telephones or comput
ers, a network could expand by allowing communication between
central switches, as shown in Figure 8.6.
In a confederation of star networks, local communication still
involves just a local switch or machine—talking on your dorm room
phone with your neighbor down the hall would use only your
school's small network. However, communication between tele
Switch 1
Switch 2
Switch 4
Switch 3
Figure 8.6
Four local star networks, connected in a network.
