[TenTec] need info on connecting 301 encoder hook-up as well as PC to Omni VI Plus

[Roger Borowski]

I recently found a model 301 encoder from TenTec's latest used equipment list and was lucky enough to see the message right after it was posted and called immediately and it was still available. 
It arrived the other day and It is in excellent condition and works fine when plugged into my Omni VI Plus. My question is how was it intended to run both PC control and the encoder? Is it one or the other or is there an adapter to add a second RS-232 type - 25 pin connector to the rig? If so, are any available anyplace that anyone can give me a lead on obtaining or do I have to homebrew one in a small project box? 
Thanks in advance, Rog-K9RB  K9RB at bellsouth.net