I do not know all the settings for PAP2T but I have configured this my SPA2102 and my alarm works #1:
Preferred Codec: G711u
Second: G729
Third: G729
Silence Supp Enable: yes
Silence Threshold: low
Echo Canc Enable: yes
Echo Canc Adapt Enable: yes
Echo Supp Enable: yes
FAX CED Detect Enable: no
FAX CNG Detect Enable: no
FAX Passthru Codec: G711u
FAX Codec Symmetric: yes
FAX Passthru Method: none
FAX Process NSE: no
FAX Disable ECAN: no
FAX Enable T38: no
FAX Tone Detect Mode: caller or callee
Call Waiting Serv: no
CWCID Serv: no
I await your news