If a Top Secret telephone calls a Secret telephone, what classification is displayed on both devices?

In the scenario where a Top Secret telephone calls a Secret telephone, both devices would display the classification level of Secret. This is because the classification system is designed to protect the most sensitive information by allowing different classifications to coexist but with the understanding that when information is transmitted, it should be secured at the lower classification level. Since the Secret telephone is only authorized to handle Secret-level information, it cannot be used to transmit Top Secret information. Therefore, the line of communication must adhere to the lower classification, which is Secret in this case. This process helps ensure that information integrity is maintained and that higher classification levels do not inadvertently compromise lower classified environments. It illustrates the principle of safeguarding sensitive information while allowing effective communication within security constraints.