[GreenKeys] Software suggestions solicited

[John Burch]

I'd like to solicit your suggestions for some software
for an "IBM-compatible" desktop computer that will 
allow it's use for RTTY operation.  Here is the situation:

The current RTTY setup consists of a "conventional"
TU - such as an ST-6 or ST-6000 or DT-600, and a
HAL communications terminal - such as a DS 3100.

What is out there in the way of software that will allow 
the desktop computer to both "transmit and receive" with
the above equipment?

Please limit your suggestions to solutions that don't
require the addition of a sound card (RITTY, MMTTY, etc).

Thank you in advance

73 de John