Greetings, It appears that some time ago, another user or two experienced similar trouble interacting w/ an ata186. For the sake of reference: http://www.mail-archive.com/asterisk-users@lists.digium.com/msg00788.html It seems like this issue was fixed at the time, any quite possibly this problem here is unrelated. In any case, I'm using a debian-testing system, gcc3.3, -O2 (just to be safe), current asterisk source via cvs, and a pair of cisco 7940's for testing. Everything looks 'fine' as far as I'm able to tell. Both phones register with asterisk, and a 'sip show peers' results in: *CLI> sip show peers Name/username Host Mask Port Status 2001/2001 172.16.0.253 (D) 255.255.255.255 5060 Unmonitored 2000/2000 172.16.0.196 (D) 255.255.255.255 5060 Unmonitored ...output (when ran with -cvvv) is: -- Executing Dial("SIP/2000-79d2", "SIP/2001|20") in new stack -- Called 2001 -- Got SIP response 488 "Not Acceptable Here" back from 172.16.0.253 == No one is available to answer at this time -- Executing VoiceMail("SIP/2000-79d2", "u2001") in new stack == Parsing '/etc/asterisk/voicemail.conf': Found -- Playing 'vm/2001/unavail' == Spawn extension (from-sip, 2001, 2) exited non-zero on 'SIP/2000-79d2' I've tried searching via google for days on this issue, and have found many discussions of what the various status codes mean (4xx, etc), but have not yet come across anyone mentioning precisely what causes this error within the context of a "real world" SIP handset. If anyone is able to offer some sort of detail to the list on this subject, I'd be most appreciative. Regards, --Tk