Complex sentence: The Backup Interceptor Control System (BUIC,) is a series of backup air defense command and control systems at sites in the United States and Canada used as backups to the main Direction Control centers of the Semi Automatic Ground Environment (SAGE) system.
Split into simpler sentences: The Backup Interceptor Control System (BUIC,) is a series of backup air defense command and control systems at sites in the United States and Canada. It was used to make backups to the main Direction Control centers of the Semi Automatic Ground Environment (SAGE) system.