asterisk users - Mar 2006 - Call Parking Grandstream

I have an asterisk setup using asterisk 1.2.4 and a mix of grandstream 
phones - BT 102 and GXP 200.

The problem I having is with call parking. Isn't it suppose to announce 
the extension where the call is being parked to the person parking the 
call at the time the call is being parked.

How ever in my setup I hear nothing but if I dial the default parked 
extension I get back the call.

Am I missing something? Or should I be using something like ParkAndAnnounce?

Thanks.

       -Alfie