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.
Asterisk cards have a different number of ports, due to the variety of needs for different applications, manufacturers try to address them. For beginners, one can request for Asterisk card with single port configured with 1 FXO module. At first, you receive the option of accept incoming calls, afterwards you can route them anywhere within your IP network. It’s only in case of a live call, and than your line is busy because you have a single FXO to handle that call.