asterisk users - Sep 2004 - Unknown IE 40 (cs6, Unknown Information Element)

what are these error messages:  Unknown IE 40 (cs6, Unknown Information 
Element)

Hi.

I see that message in console.

    -- Zap/1-1 is ringing
!! Unknown IE 40 (cs6, Unknown Information Element)
    -- Zap/1-1 answered SIP/1016-e34b

As see in older messages it some Information send by phone station to my via
PRI.
But what does IE 40 mean? I cann't find information element 40 (as in know
in hex) in documentation.