SIGNALLING 

 This option when enabled causes any Channel Signalling feature that the
 radio may have to be enabled.  This includes Unit Identification,
 Singletone, and DTMF decode (NTN 5697).  The DTMF encode feature is
 enabled on a radio wide basis in the Sig/DTMF screen.  Note: The 
 radio must be equipped with the appropriate front cover to operate 
 properly.