First: on the remoterig 1258 put a stereo, 1/8″ splitter. Then route one stereo plug to your sound card input, and the second one will go to your speaker or headphones.
now if you remember when you first set up your remoterig, you used a miniature sub usb connector, to a regular USB connector that you connected to your computer to program the RRC 1258. You will once again use this same connector to generate FSK for RTTY.
second: take the sub USB connector and hook it up to the small USB plug, right below the power led. And plug the other end into an empty USB port on your computer. As soon as you do this your RRC will make 4 more virtual com ports on your computer. On mine it made. RRC 1258 com0. Com3. And three other ports. The only one that is important is the on that is labeled, RRC 1258. COMExtra, COM7 in my case. It will always make the RRC 1258 com extra port, but the important thing to right down is the com port number it makes. You can see this in Device manager under ports.
Third: Start MMTTY or any favorite terminal program for Rtty. Go to the sound tab and select your sound card on the left side that you have hooked up to your RRC. On the right side go down below the last listed sound card and put a dot next to a sound card that does not exist. This tells MMTTY that you will transmit with something other than a sound card. No go to TX tab, and under port, put the number of the serial port that shows up next to COMExtra, in my case I chose com7. Nothing else on this page. Go to misc tab bad select com-txd (FSK). Then hit the USB port button, when next menu comes up hit C, limiting speed. You are now done.
Connect to an RHR site, set K3 to DATA, then select FSK-D, 45 baud, the field will change Data on the RHR site, and you are now set to go. just bring up MMTTY, tune to the receive frequency, decode as usual, and if you set macros in MMTTY, you just hit one and it will generate the PTT signal as well as the Diddles for RTTY.