What does a "no display" indicate in a communication system?

A "no display" in a communication system typically indicates a difficulty with the transmission and retrieval of data, particularly in the context of an Automated Location Identification (ALI) system. When there is no data displayed, it suggests that the system is failing to retrieve or present the necessary information needed for effective communication or response. This could result from various issues, such as technical malfunctions, connectivity problems, or data retrieval errors.

In contrast, successful data transmission would result in the display of the relevant information, while activation of emergency mode and normal operation would also generally produce some form of visible output or indication on the screen. Therefore, a blank screen without any ALI data signifies a problem that needs resolution.