I have a AS5400 as our local SIP gateway with 6T1, I would like set up sip client to fail over to another SER proxy that can route to local PSTN when AS5400 capacity is full. Can the AS5400 return special error code or sip signal to sip client?

we have a AS5400 already installed a CT3 card, but only use 12 T1. So can we install other two 8CT1 card on this service to use together(because we have a contract with different telecom service provide)?

I have a cisco as5400 as voip gateway, when call coming in from PSTN T1, the gateway send invite to our sip server, the sip server send back 100 trying, but didn't send back 180 trying within about 10 seconds, the cisco send cancel to sip server to e...