Thanks for posting! Unfortunately, the ADTRAN TA900 series cannot ring two ports simultaneously from a single received SIP Invite. However, it is possible that the SIP server may support some type of "ring all" ring group. In this scenario, a given call would actually result in the SIP server sending the ADTRAN unit two separate SIP Invites, one for the phone and one for the number associated with the external ringer. The ADTRAN unit would then ring both ports. When the call is answered by called party, the SIP server should then send a SIP Cancel for the external ringer.
Hope this helps,
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