You may still be able to get a wave of sorts with one unit.
The instructions are on page 18 and 23 of the manual. Page 23 is the more user-friendly one I find as it's actually spelled out
Here it is if you don't already have it. I'd suggest you save it as it's 8.33 meg .... pain to open on the web
http://ecotechmarine.com/wp-content/...vision1.11.pdf