Information on the "checker screen" comes from the antennas. It tells of any antenna errors: temperatures that are out of range..........Any information that appears on the checker screen also is printed on the line printer. The line printer is old and noisy but it serves the purpose of alerting the array operator (by its noisy printing!) that something has appeared on the checker screen that may need the operators attention. Many of the operators get so used to the sound of the printer that they can tell by the sound what information was just printed.