We already bring the Raspberry Pi to the telecom area. We have been made two different modules, one is PiTDM which is gain your Raspberry Pi to be able to connect to traditional PSTN lines, such as FXS or FXO lines. Another one is PiGSM which is let your Raspberry Pi gain to be able to connect to the mobile network, such as 2/3/4G voice mobile network.
The Asterisk recognized the PiTDM and PiGSM as standard Dahdi channels, you can dial or answer calls like normal asterisk channel.
With PiTDM or PiGSM module, your voice call can pass through the PSTN or GSM telecom network, you can build a real worldwide telecom network with cheaper and fantastic Raspberry Pi board (2 or 3 version)!
For more information and how the PiTDM and PiGSM work with Raspberry Pi board, please check it out on our website :