I need to find a recent and neutral comparison of the major products
available to connect an Asterisk server to the telephone network,
whether ISDN (BRI) or PSTN, and through a PCI card or some external
box. I’m told there are less issues (echo, stability) with external
boxes compared to PCI cards.
Apparently, the main brands are Digium, Sangoma, Rhino Equipment,
Patton, and Audiocodes.