[TenTec] OMNI VI Plus, MMTTY, and FSK

[KA5M@aol.com]

Ed, I'm just getting started on FSK RTTY, and want to understand the basics 
of the radio to computer interface.  How does a signal from TXD (pin 3) of a 
DB9 serial port connector, through a 1K resistor, to Mark/Space on the rear of 
the OMNI VI Plus, put the transceiver into FSK transmit?  My limited 
understanding is that all Mark/Space input on the rear does is control which tone, Mark 
or Space, is being sent.  What am I missing?

Also, which schematic are you referring to?

73,
Marsh, KA5M