SCH1968
Key 0 must be a DN key on an i2004 set (I.e. one of SCR SCN MCR MCN PLN
PLR ACD DN).
SCH1970
Message Waiting Key (MWK) must be defined on key 16 on an i2004 set.
ITG Line 2.0/i2004 Internet Telephone Description, Installation, and Operation
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