What action will trigger the extension of cylinder 2A in the control circuit context?

The action that triggers the extension of cylinder 2A in the control circuit context is the activation of proximity sensor 1B2. Proximity sensors play a crucial role in automated systems by detecting the presence or absence of an object, or its position. When the sensor is activated, it sends a signal to the control system, indicating that it is time to engage the cylinder. This interaction is essential in controlling the motion of the cylinder effectively, as the control circuit relies on sensor inputs to dictate its operations.

In contrast, mechanical pressurization might engage the cylinder but does not directly relate to the control system's electronic signaling. Shutting down the system would halt all operations, including cylinder movement. Similarly, increasing the volume of fluid could affect cylinder operation but does not inherently dictate the extension unless paired with specific control signals, such as those from the proximity sensor.

Therefore, activating proximity sensor 1B2 is the clear action that triggers the cylinder’s extension in the context of the control circuit.