Yeastar S20 (last firmware) with one card ISDN BRI on board.
Trunk BRI1 (Network)
Trunk SIP Register trunk
Inbound Routes: ISDN to SIP, SIP to ISDN (Destination: Outbound Route)
Outbound Routes: ToSIP, toISDN
I Have a ISDN PBX connected on Bri1 (Or a simply ISDN Phone)
When External user call Sip number, the ISDN Phone Ring and work
When the ISDN Phone call out , i hear Busy tone immediately.
How can i resolve ?
Thanks so much