The original dual band CTCSS for this radio was the Kenwood TU-4C option,
which were 2 encoders stacked on top of each other.
It does not appear that Piexx makes a direct replacement (you can ask them).http://www.piexx.com/index.php?main_page=index&cPath=6
Kenwood TW-4000a - Universal Radio listing of accessories http://www.universal-radio.com/CAtal...s/tw4000a.html
The current internal Com-Spec model is the: SS-64http://www.com-spec.com/insheet/ss64inst.pdf
The TE-32 is the SS-64 encoder in an external PacTec enclosure with a tone selection knob.
It appears that you would need 2, or ability to inject CTCSS at a common point (schematic needed) in order to emulate the Kenwood TU-4C option.
Communication Specialists never wrote a specific application note for the TW-4000a.