You are supposed to be able to connect the H.323 Gatekeeper to a PSTN gateway. However, there is NO docs anywhere on how you would do this. I don't have access to such a gateway. Too bad, because it would be an interesting project.
I will be testing this myself soon, what I have in mind is installing an ISDN router as secondary connection(primary is a 2Mbit pipe), which I have patched straight in to the PBX, this is an ISDN 2 line off an index switch channeled down isdn30e pri. Don't know if it will work yet, if it does I'll let you know the procedure.
It does work through a PBX, same config as my post below. Although, unless you have unmetered access it proves very expensive. The only connections I have tried are ISDN and modem,but I am sure an ethernet presented DSL or cable modem will work. VOIP seemed to work OK, with no probs with the www, going through the 2mb pipe.Phone and VPN? I am not sure what you are trying to achieve, but there is a lot of hardware\software out there to meet this end. I suppose all this would depend on what PBX you are running too. Aside from that, HD53C caught me in the server room flustered with 3 phones on the go,talking into the earpiece of one. LOL. I shall not discuss his DNS config out of politeness SR
I have FXO and FXS gateways connected via ISA Server gatekeeper. Gateways are from D-Link. It works fine from PBX and from NetMeeting. But unfortunately there is no any monitoring for the gateway, log file for example.