[TenTec] Transmit control with no interface

[John Graves <jh.graves@verizon.net>]

I am trying to operate digital modes without an interface with my 
Jupiter.and  I can copy both psk and rtty very well using Ham Radio 
Deluxe and the mmtty engine inside N1MM as well as free standing. 

I had hopes of using VOX but cannot get it to trigger.  I have selected 
VOX on the front panel and am using the accessory cable to connect to 
the back jack so I have selected line as the audio source.  I moved the 
Vox Gain all over the map with no results.
Is there anyone who is operating this way that can tell  me how they 
have set up to make it work??