asterisk users - Aug 2007 - Polycom Phones Call Hold Reminder function problem

I want to enable on hold  reminder function on polycom 430 phones. I have
enabled it in sip.cfg
using this setting 

 <hold>
         <localReminder call.hold.localReminder.enabled="1"
call.hold.localReminder.period="60"
call.hold.localReminder.startDelay="90"/>
 </hold>

But still if the call is on hold the phones does not remind about the on hold
call.
Any idea?????????????
Regards
Farooq
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