Each of the two ports on a two-way valve is alternately used to permit flow as well as close it off. A two-way valve can be specified to be either “normally open" or “normally closed” in its operation. With a normally open valve, the valve remains open until some type of current is applied to close the valve. Suspension of the electrical power causes the valve to automatically reopen to its normal state. A normally closed solenoid valve is the most common, working in the opposite fashion, remaining closed until a power source causes it to open.