What does AND logic require?	Every required input must be active. Series normally open contacts are a common implementation.
What does OR logic require?	At least one of the inputs must be active. Parallel normally open paths are a common implementation.
What is NOT logic?	The output is the opposite of the input. A normally closed contact can invert an active-true signal.
What is NOR logic?	The output is ON only when neither input is active.
What is NAND logic?	The output is OFF only when every input is active.
What is the normal state of a contact?	Its position when its associated operator or coil is not actuated.
What does NO stand for?	Normally open: no conducting path in its normal state.
What does NC stand for?	Normally closed: a conducting path in its normal state.
What is a seal-in circuit?	An auxiliary contact maintains the command after a momentary START signal is released.
What is a holding contact?	An auxiliary contact, often NO, used to keep a relay or starter energized.
Why is STOP typically NC?	Opening it interrupts the control path; it also tends to fail open on a broken wire.
Why is START typically NO?	The operator must press it to initiate the start command.
What does an overload contact do?	It opens the control circuit when the overload device trips, removing the starter command.
Does overload protection normally replace a short-circuit protective device?	No. Overload and short-circuit protection serve different functions.
What does a motor starter coil do?	It operates the starter contactor when correctly energized.
What does a pilot lamp indicate?	The electrical status of the point or contact controlling it; it does not always prove mechanical motion.
What is a selector switch?	A maintained control switch used to choose operating modes, such as HAND, OFF, or AUTO.
What does HAND mean in a pump selector?	A manually selected run command, still subject to required protective interlocks.
What does AUTO mean in level control?	Operation is governed by level signals and the intended control sequence.
Why use a high and low water threshold?	The separation creates hysteresis and prevents rapid starts and stops near one level.
What happens at the low-level threshold in a fill system?	A start request is generated when the liquid falls below the lower setpoint.
What happens at the high-level threshold?	The fill pump is commanded to stop when the liquid reaches the upper setpoint.
What is an auxiliary contact?	A contact mechanically or electrically associated with a relay or starter, used for control or indication.
What is the difference between wire and terminal numbers?	Wire numbers identify electrical nodes; terminal labels identify physical connection points on devices.
What is a control transformer?	A transformer providing the voltage needed by a control circuit from an available supply.
What is a virtual voltmeter reading across a healthy closed contact?	Approximately zero volts when both sides are at nearly the same potential.
What might a meter show across an open contact?	Approximately source voltage if a complete return path exists through the load.
Why can an open return path confuse voltage readings?	Floating conductors and high-impedance meters can yield undefined or misleading readings.
What does line-to-line control voltage mean?	The potential difference between the two control supply conductors.
What is the first rule of electrical fault-finding?	Use an approved safety procedure, establish expected values, and verify the source before tracing downstream.