Telephone ISDN can not call out


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

Simone Zerbin


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