HUT Comms. Lab, Timo O. Korhonen
22
Example: PSTN Network operator in two towns
PBX: Private Branch Exhange
MUX: multiplexer
RLL: Radio in the Local Loop
NMC: Network Maintenance
         Center
X.25
OSS: Operations Support
        System
ATM
A PCM-link
Note that by dial-up
networking part
of local exchange capacity
is allocated for another
operator