Configurations
of GSM/VoIP networks allow the service providers to avoid the local Wired
Public Switched Network (PSTN) in communication with a GMS mobile handset. As a
result, the high rates charged by telephone companies are avoided.
Citel PBXgateways are installed at the central PBX location, and EXTenders are deployed at branch offices, call centers, or at home offices over managed IP connections, DSL, cable, or analog circuits