This is the TTY output connector on the back of the 1278. If we have an FSK input jack on the transceiver, then what we do is run a wire from the output pin on the 1278 labeled "FSK" (the 3rd one from the right) to the FSK input on the back of the transceiver. Then run a wire from the "GND" pin (3rd from the left) to a convenient ground on the transceiver. This way, the 1278 serves only to signal the transceiver when to switch from "Mark" to "Space" and never really supplies a signal to be transmitted. The transceiver, using the FSK mode, automatically synthesises the proper signals. Oh, and by the way, the 1278 comes with a plug that fits over this output connector. If you have lost yours, then go to an electronics shop, take your 1278, and show them what you need. I'm sure they can round up one for you.
I have noticed a dramatic difference in the ease in which I work RTTY and
PACTOR contacts since I converted over. If you have the connections on the
back of your radio, go ahead and make the change!! You'll be glad you did.
Now, what if you don't have that wonderful FSK jack?