Emergency Broadcast System - Activation Procedure

Activation Procedure

Actual activations originated with a primary station, which would transmit the Attention Signal. The Attention Signal most commonly associated with the system was a combination of the sine waves of 853 and 960 Hz, an interval suited to getting the audience's collective attention due to its unpleasantness on the human ear. Decoders at relay stations would sound an alarm, alerting the station operator to the incoming message. Then each relay station would broadcast the alert tone and rebroadcast the emergency message from the primary station.

A nationwide activation of the EBS was called an Emergency Action Notification (EAN). This was the only type of activation which broadcast stations were not allowed to ignore; the FCC made local civil emergencies and weather advisories optional (except for stations that had agreed to be the "primary" source of such messages).

To activate the EAN protocol, the AP and UPI wire services would notify stations with a special message. It began with a full line of X's, and a bell inside the Teletype machine would sound ten times. To avoid abuse and mistakes, the message included a confirmation password which changed daily. Stations that subscribed to one of the wire services were not required to activate the EBS if the activation message did not have proper confirmation.