Nokia 12 GSM MODULE REMOTE I/O Control Manual page 14

Characters accepted for the message identifier are defined in Chapter 7, except
the space characters.
Note: You cannot use the Remote I/O control if there is no message identifier
defined. In this case, all received short messages will be handled as normal
messages and the inputs/outputs cannot be controlled in the Remote I/O control.
Note: The message identifier is 1-8 characters long and case sensitive.
Figure 2. User Control Mode dialog
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