BAUDOT F7BBN / 2 channel ITA-2 RTTY
This is a 2 channel simplex asynchronous BAUDOT signal also referenced as TWINPLEX. Its form, according to CCIR Recommendation 346-1, is: "4 Frequency diplex systems"
(Dusseldorf, 1990). This is a 2 channel 4 tone diplex asynchronous signal usually consisting of 2 channels of ITA-2 baudot running at the same speed (or according to Rec. 346-1 1 channel baudot/1 channel morse code). According to the recommendation both channels are often scrambled and no loggings of this form have been found to date.