What does 'normal open' mean in circuit protection?

In the context of circuit protection, 'normal open' refers to a switch configuration where the contacts are open when the switch is not activated. This means that under normal conditions, there is no current flowing through the circuit because the path is incomplete. When the switch is activated, it closes the circuit, allowing current to flow. Thus, 'normal open' indicates that current only flows when the switch is intentionally engaged or activated, which is crucial for applications where it is important to control when power is supplied to a part of the circuit. This functionality helps in protecting the circuit by ensuring that it remains off under normal circumstances, protecting against accidental overload or short circuits.