Hello, I have a Kenwood TM-721 E in operation here. Now I found the CTCSS UNIT TSU-6 while cleaning up. (CTCSS unit TSU-6, TM-621A / 721A only). There is a slot for this in the TM-721E. The TM 721 E does not have the Tone or T.SEL button for operation. Unfortunately I have not found anything on the Internet. Does anyone have a tip on how I can still use the CTCSS unit in the device?