Icom IC-U68 - OPTIONS INSTALLATION; The UT-86 TONE SQUELCH UNIT provides subaudible tone encoder and tone squelch functions (the transceiver has a built-in subaudible tone encoder which provides an 88.5 Hz tone only).; The UT-88 VOICE SCRAMBLER UNIT provides a voice scrambler function for private communications as well as subaudible tone encoder and tone squelch functions.