Here are the format of SMDI messages used with MWI On/Off :
MWI On
OP:MWI<0X20>”stn-num”!<^D>
OP is used to indicate that MWI should be turned on for the specified station number and <^D> indicates an end of transmission.
MWI Off
RMV:MWI<0X20>”stn-number”!<^D>
RMV is used to request that MWI should be turned off the the specific station number