What is a normally closed switch and where is it used?

A normally closed switch is a type of electrical switch that maintains a closed (on) position until it is actuated. In its default state, current flows through the circuit. When the switch is pressed or triggered, the connection opens, stopping the current. This type of switch is widely used in safety systems, industrial controls, and emergency stop circuits where immediate disconnection is necessary when a condition changes. For example, in a safety door mechanism, the circuit remains active as long as the door is shut. The normally closed switch plays a crucial role in fail-safe designs, ensuring that equipment stops if connections are disrupted. Its reliability and fast response make it ideal for both electronic and mechanical systems requiring consistent control and safety.