You’ll notice that each site operated on multiple frequency pairs across the HF spectrum. This was for two reasons. First, each channel could only handle one call at a time, and so this allowed for more simultaneous traffic. Second, not all frequency bands were usable (due to atmospheric and geomagnetic conditions) at any given time. So in practice, at most half a dozen or so ships PER OCEAN could use the system at any moment.

Multiple transmitters shared the antennas using tuned combiners.