A cable tester is a device used to check the integrity and functionality of electrical cables, particularly those used for networking and telecommunications. It helps identify issues such as short circuits, open circuits, and miswiring, ensuring that cables are properly connected and functioning as intended. These testers are commonly used by technicians and engineers in the field of telecommunications and networking. They can test various types of cables, including Ethernet and coaxial cables, making them essential tools for maintaining reliable communication systems.