I want to know the details of control of the ZK2 series ejector with energy saving function.

In the case of PNP specification, when you close (ON) the contacts between the brown (DC positive) and gray (FUNC) wires, the output that opens the supply valve from OUT2 via the main circuit of the vacuum pressure switch is generated, and vacuum suction takes place.
When the vacuum increases to the specified value, the output from OUT2 goes OFF automatically on the main circuit side, and the supply valve closes momentarily.
The vacuum is held in this condition. However, when the vacuum falls to the set pressure, OUT2 once again generates an output, and the supply valve opens.
The suction operation continues until the contacts between the brown and gray wires go OFF.
When the vacuum is released, the contacts between the brown and gray wires are turned OFF, and also the contacts between the white (input for release valve) and the brown (DC positive) are turned ON.
In order to hold the vacuum, the check valve inside ZK2 is double, thus preventing the vacuum from being broken unless the release valve is opened.