Thanks alicic. That was most helpful.
I have a follow up question -
With the setup described, I would use 4 analog ports off the hardware-PBX (HPBX) to the Gateway. I quess that I would assign those ports extensions (e.g. 4000, 4001, 4002, 4003). Would those 4 extensions be the only 4 that could be used on the 3CX, or would those end up being the 'trunks' connecting the HPBX and 3CX? Limiting me to 4 concurrent connections between the HPBX and 3CX, but unlimited extensions registered to the 3CX.
Or do I misunderstand?
Thanks again.