SIGNALLING 

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