What does an secondary interlock switch do in a microwave oven?

A secondary interlock switch in a microwave oven serves as a safety feature that ensures the oven cannot operate when the door is open. It works in conjunction with the primary interlock switch to prevent microwave radiation from escaping and to protect users from exposure. If the door is not securely closed, the secondary interlock switch interrupts the power supply to the microwave's magnetron, effectively disabling the oven. This redundancy helps enhance user safety during operation.