When connected to a VacuFlush toilet, you may only use Purasan model PST1203 - other Purasan models won't work. The Purasan is installed completely independent from the VacuFlush toilet. A solenoid valve is supplied with it, that taps into your pressurized water system, to provide water to the halogen canister, and is wired to the Purasan's printed circuit board. When the button is pressed to turn on the Purasan, the Purasan's printed circuit board causes the electrically-operated valve to open for a pre-set period of time, to allow pressure water into the canister. This water dissolves a small amount of the chemical inside the canister, and then drains into the Purasan treatment box by gravity, carrying the chemical with it. The canister must be mounted a minimum of 15" above the treatment box proper (higher is OK, but it must not be lower than 15"). Then you install the rest of the Purasan system, with a control panel in the head. You press the button on the control panel to start the Purasan, then flush the VacuFlush toilet (step on the pedal or press the switch button on the VacuFlush, depending on the model). The Purasan will then run for 2 minutes and shut off.
Or, it can be made a completely automatic operation by splicing into the switched wire on the vacuum pump's motor. From there you run a wire to one of the terminals on the Purasan's printed circuit board. Then, when the vacuum pump comes on, it sends a 12 volt pulse to the Purasan, starting it. That is the only physical wiring connection that needs to be done to the VacuFlush; the rest of the Purasan system is wired independently of the VacuFlush. The solenoid valve and the canister are mounted and operate the same as described above.