A cable tester is a device used to check the integrity and functionality of various types of cables, such as Ethernet or coaxial cables. It helps identify issues like broken wires, shorts, or incorrect wiring configurations, ensuring that the cables can transmit data effectively. Typically, a cable tester consists of two main parts: a main unit and a remote unit. The main unit sends signals through the cable, while the remote unit receives them. By analyzing the results, users can quickly determine if a cable is working properly or if it needs repair or replacement.