Relays are vital components used in electrical and electronic systems to control the flow of current through a circuit. They serve as electrically operated switches, allowing low voltage signals to control high-power circuits. In communication systems, relays are frequently used to isolate different parts of the system and to ensure signals are transmitted properly. Testing these relays ensures they are functioning correctly and are not the cause of signal disruption. A multimeter, a handy tool for measuring voltage, current, and resistance, is essential for troubleshooting relays. In this article, we will explore how to test a communication relay with a multimeter, focusing on the coil, normally open (NO), and normally closed (NC) contacts.