What are the descriptions of the types of pneumatic angle seat valves?

Pneumatic angle seat valves are mainly divided into two categories:
1. Two-way action pneumatic angle seat valve: When the gas enters the actuator from one port respectively, the valve stem acts to drive the piston to open the angle seat valve. When the gas enters the actuator from the other end, the valve stem drives the piston to close the angle seat valve.
2. One-way action angle seat valve: When the angle seat valve is normally closed, the gas enters the actuator compression spring to drive the valve stem upward to open the valve. When the angle seat valve is normally open, the gas enters the actuator and the tension spring drives the valve stem to move downward to close the valve.