Many water treatment end users can wind up inheriting an orphaned treatment system. Usually it was part of a package supplied by a car wash or a boiler treatment company. The situation becomes more confusing when there are multiple tanks with elaborate wiring and piping that resembles knotted intestines. Also, the owners manual provides little guidance or is lost. The following will provide a link to enlightenment and will help ID your multiple tank system and un-knot your intestines.
In the days before reliable electronics, softener manufacturers demanded Fleck design a control valve system that could operate multiple tanked softeners and filters. Fleck labeled them "systems" and assigned them an elaborate numbering ID System 4,5,6,7 & 9. What no 8?
Confused? Here is the link to Pentair Fleck Valve enlightenment.
For a minimal cost you can convert the "Wire Monsters" to state of the art electronics by adding NXT power heads.
The NXT have all these systems plugged in. Just select the one you need. Also here is information on the Aquamatic 962 NXT controller.