What is the meaning of the letter S in PIES?

• A. Sensor
• B. Switch
• C. Safety
• D. Stimulus

Answer: (B)

The S in PIES represents Switch—the action of operating the control that changes the circuit’s power state. In this mnemonic, the steps build toward actually altering power: identify the power source, ensure it can be safely isolated, verify the environment is safe, and then use the switch (or circuit breaker) to disconnect or reconnect power as required. The switch is the physical action that completes the sequence; without flipping the switch, power remains on even if you’ve checked the other factors. The other terms are nouns describing components or concepts, not the action that changes the electrical state.