When you have two PABX in the different sites, you hope their extension can call each other, you can refe to the below method.
The related information is like this:
site 1: extension 6001-6009 site 2: extension 7001-7009
the call process is:
1. in site 1, when any extension of PABX1 dials the number starting with 7, the call will go out through FXO 1.
2. when gateway 1 reaches the call of FXS 1 , gateway 1 can transfer the call to gateway 2 through Internet;
3. when the gateway 2 receives the call from gateway 1, the call will go out through the FXO 1 of gateway 2;
4. the call will go to the specific extension of PABX2.
At the same time, the call of site 2 is similar to site 1.