What is the purpose of an EOL resistor in a circuit?

The purpose of an EOL (End-Of-Line) resistor in a circuit, particularly in security and fire alarm systems, is to allow operation with a designed system current. This resistor is used at the end of a wiring loop and serves to monitor the integrity of the circuit. When properly installed, it helps ensure that the system can detect faults like short circuits, open circuits, or other issues affecting the circuit integrity.

By maintaining a specific resistance value at the end of the loop, it ensures that the current through the system remains at the intended level. This is crucial for reliable operation and accurate signaling, as the system can identify whether the line is intact or compromised based on the current feedback it receives. An EOL resistor effectively creates a known reference point that enables the system to function correctly as designed, thus ensuring safety and reliability in applications such as fire alarms and security systems.