The signal spreads on a ~600 Hz bandwidth, each tone is 100 msec length. Manipulation speed is 10 Hz. The traffic sent by this system seems consist of 5 figure groups and 1 space character tone. Looking at the grid, the signal shows 14 tones, spaced by 40 Hz, with two empty spaces so the used tones are reduced to 12: the lower tone used for the space chars and the other 11 tones for coding the five figures groups (55 combinations).
Any idea?


