I have a customer where we are putting an Asterisk PBX in front of a legacy (non-VoIP) PBX. One of the requirements it that the Asterisk PBX have 2 PRI ports (one towards the legacy PBX and one towards the carrier) with the ability to go to pass through should the Asterisk PBX (software or hardware level) fail.
I did not see this feature in the Digium, Sangoma, Allo, or OpenVox cards.
Does anyone know of a card that will do this? I know that Digium has an external box (the r850) that does something similar for 2 PBXs making them high availability, but in this case I only have the 1 Asterisk box acting as a gateway and passing some calls out over SIP and IAX2.
Any suggestions would be appreciated.