Recently I thought about Morse Code and Ternary and found that it is easy to represent this code in balanced ternary form - lets use N (negative) for "dash", P (positive) for "dot" and O (zero) for space. We don't need space between dots/dashes because we already can differentiate them, but we still need single space between characters (series of dots and dashes) and double space between words:
On this image you can see conversion of words to ternary morse code and reverse transformation to the actual morse code (it's longer because dash should be longer than dot).
As use can see in the beginning we have special abbreviation KA/ that means "starting signal" (other meaning is CT/ "Commence Transmission") that allows the receiver to adjust receiving speed for further message (actually any start where we have alternating "dashes" and "dots" will work the same way, for example CQ). After message finished (lets say if receiver got more than 5 spaces), speed settings should be cleared.
Then I got an idea how to use it as serial communication between ternary devices - we can use cheap handset cords (with reversed wires):
We need Rx signal, Tx signal and Ground signal. Because wires are reversed, we should put grounds on two of them and other two will have Rx and Tx that connected Tx and Rx respectively on the other side:
Plug side will look like this: