What should you check if there is hum on a customer's telephone line?

If there is a hum on a customer's telephone line, it is essential to investigate potential issues related to interference and signal integrity. Checking for shielding problems in the wiring and poor terminations is crucial because these factors can significantly impact the quality of the telephone line.

Shielding issues can lead to electromagnetic interference being picked up by the wiring, which may result in a hum or noise being heard in the call. Additionally, poor terminations—where the wires connect to the terminals—can create discontinuities in the electrical connection, resulting in hum or other unwanted noises. Ensuring proper shielding and high-quality terminations is vital for maintaining clear and reliable voice communications on telephone lines.

In contrast, simply checking the connection to the telephone exchange focuses on the external aspect and may not address internal wiring problems. Evaluating the speaker volume or the type of telephone used is unlikely to resolve underlying wiring issues, which are the most probable causes of the hum in this scenario.