The Primary Alerting System (PAS), was a network of land-line connections used by the Strategic Air Command (SAC) for command and control of its nuclear forces. PAS provided immediate and simultaneous voice communications to all (SAC) unit command posts and missile launch control facilities.

PAS reached each Command Post by two geographically diversified circuits; one circuit, commonly called the "front-door" circuit tied the unit directly to Headquarters (SAC); the other, or "back-door" circuit provided a link to the parent Numbered Air Force.