What does E1 display code represent on the KYV-5?

The E1 display code on the KYV-5 represents the absence of a Traffic Encryption Key (TEK). This code indicates that the encryption device is not properly configured or that the TEK needed for secure communication is not available. In a secure communication environment, having a valid TEK is essential for maintaining the confidentiality and integrity of the transmitted information. Thus, the appearance of the E1 code serves as a critical alert to users that they cannot engage in encrypted communications until a proper TEK is sourced and input into the device. The other codes listed do not pertain to the absence of TEK, focusing instead on different operational statuses.