Testing a communication relay is an essential task for ensuring the proper functioning of electrical systems, especially when troubleshooting or diagnosing faults in communication circuits. A multimeter, a versatile and indispensable tool, allows you to check the condition of a relay by measuring the resistance and voltage at various points. In this guide, we will walk you through the process of testing a communication relay with a multimeter, covering both the physical and electrical aspects of the relay, step by step.

1. Understanding the Communication Relay Before diving into testing, it’s crucial to understand the basic components and function of a communication relay. A relay is an electrically operated switch, used to control circuits by opening or closing the contacts in response to an external control signal. In communication systems, relays are often used to route signals or provide isolation between different parts of a system. Typically, a relay consists of two main parts： Coil： This is the electromagnet that, when energized, activates the relay. Contacts： These are the switching elements, which may include normally open (NO) and normally closed (NC) contacts, as well as a common (COM) terminal.