If your voice quality is not very good due to the bandwidth available for VoIP, then you may consider to install G729 on your Asterisk box. You can use the following link to install the G729 for your system for the purpose of codec evaluation.
Celeron is Pentium3/Pentium4/Core with smaller cache.
How to check whether your system is 32-bit or 64-bit of your Debian system?
Since my Debian system is a 32-bit OS sys, I went to the link [1] and under ast13 directory, I obtained the file "codec_g729-ast130-gcc4-glibc-pentium4.so". I renamed it to codec_g729.so. I used the command "scp codec_g729.so root@10.0.88.14:/usr/lib/asterisk/modules". After the remote copy operation completed, I ssh to the remote site using the command "ssh root@10.0.88.14". It asked me to enter the password. I went to the directory /usr/lib/asterisk/modoules and chmod 755 codec_g729.so. Restarted the asterisk and issued the command "core show translation recalc 10", I got the following figure
There is no difficulty for those items, except the installation of G729. I failed to make connection by scp. But finally, I find a tool "pscp.exe" that can copy the file from PC to Debian. Attached the video for your reference.
Now you are able to compile your own Asterisk 13 on Debian 8.1. You are able to do a lot of things but there are still many things that you have to learn. For instance,
1) how to integrate your Obi110 into your Asterisk system?
2) how to group your outbound trunks into a single out-going dial plan?
3) how to register the public voip SIP account?
4) how to handle incoming phone calls?
Workshop 6 has already completed. The next Workshop 7 is the first workshop which lets you connect a trunk to external PSTN service via the Asterisk box. It allows both the outbound/inbound services from/to selected users.
The Workshop 7 was just finished. It shows the way to configure the OBi110 such that the outbound call (PSTN, SP2) via the remote OBi110 could be realised.