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The diagram you've provided shows the basic parts of a PLC (Programmable Logic Controller) system and illustrates how input and output devices are connected. Let's explain the input and output symbols in the diagram:

Input Symbols:

1. Push Button:
   • Represented by a circle with a cross inside it.
   • It is a simple switch that can be pressed to complete a circuit, sending a signal to the PLC.
2. Limit Switch:
   • Shown as a rectangle with an actuator symbol (e.g., a lever).
   • It is a type of switch activated by the physical movement of an object, providing input to the PLC.
3. Proximity Sensor:
   • Depicted as a rectangle with an arrow pointing towards it.
   • It detects the presence of objects without physical contact and sends signals to the PLC.

Output Symbols:

1. Motor:
   • Represented by a circle with the letter "M" inside it.
   • The PLC sends signals to start or stop the motor.
2. Lamp:
   • Shown as a circle with a light bulb symbol inside.
   • The PLC can turn the lamp on or off based on its programming.
3. Solenoid Valve:
   • Depicted as a box with lines indicating fluid control.
   • The PLC sends signals to control the opening and closing of the valve.

Explanation of the Diagram:

1. Input Sensing Devices:
   • These include various input devices like push buttons, limit switches, and proximity sensors.
   • When activated, they send electrical signals to the Input Module of the PLC.
2. Input Module:
   • Converts the input signals from the input devices into a format that can be processed by the PLC's CPU.
   • Provides optical isolation to protect the CPU from electrical surges.