asterisk users - May 2008 - Newbie Polycom: Cannot Disable Services button

I was able to disable the DND button (no 9) on IP60x by putting the
following line in sip.cfg.

   <keys key.scrolling.timeout="1"
    key.IP_600.9.function.prim="Null"/>

However, I could not do so for the Services Button (no 29) on IP600 (or
Applications button on IP01)

   <keys key.scrolling.timeout="1"
    key.IP_600.29.function.prim="Null"/>

It seems like SIP admin guide did not include "Services" as the
function
that can be modified.

Anyone having the same experience?