[Asterisk-Users] cannot change distinctive ring polycom phones

[Giorgio Incantalupo]

Hi,
I'm using asterisk 1.2.1 on a debian sarge distro.
I've followed notes in
http://www.voip-info.org/wiki/view/Polycom+auto-answer+config
and
http://www.voip-info.org/wiki/index.php?page=OptiPoint+600+SIP+-+Distictive+ring+using+ALERT_INFO
but I still cannot change ring style via asterisk using
exten => 666,1,SipAddHeader(ALERT_INFO="ring3")
in extensions.conf .

Is it possible to do it on polycom ip phones? If yes...how? Is there 
something missing??

TIA

Giorgio Incantalupo