An SPDT relay, or single-pole double-throw relay, is an electromechanical switch used to control the flow of electricity in circuits. It has one input (pole) and two outputs (throws), allowing it to connect the input to either output. This switching capability makes SPDT relays useful for routing signals, toggling between devices, or providing redundancy in security systems. In cybersecurity and electronic security, SPDT relays are often used to control alarms, locks, or other critical devices, ensuring that signals are directed appropriately based on system logic or detected events.