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Whether it sends the 183 with or without SDP, or whether it even sends a 183, is controlled by the Sonus SBC 1000/2000's internal, pre-programmed translation table. The internal translation table controls the translation for ISDN Progress/Alert/Connect messages, as well as SIP 18x/200 messages for calls ISDN ? to SIP, SIP ? to ISDN, and SIP ? to SIP.
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