By Jim Tharp

The Emergency Alert System is a system that is used to notify the public of pending emergencies or hazards. It’s the link between government agencies that are tasked with managing emergencies and broadcasters. It’s best utilized when government agencies have important information and needs to get that information to the public in as rapid a method as possible so as to save lives and property. Events that build slowly and have wide news coverage are not usually the type of events where the EAS is of much value.

Washington State has one of the best and most effective EAS plans in the Nation. The whole thing is laid out in the Document "State of Washington Emergency Alert System. EAS Plan". This is dated March 3, 1997 and was approved by the Governor of the state and by the FCC. The plan is quite lengthy. This is a boiled down explanation of that plan.

The EAS system was designed with the concept of being compatible with the National Weather Services SAME encoding scheme. When an alert is issued it is stamped in a digital format and has an Address, Event Code, Time, Duration, and, Originator Code. A verbal message (up to 2 min.) is added to explain the exact circumstances of the alert. This whole package / message is sent through out the system. The magic of creating this message is all handled in the EAS encoder.

An EAS alert then consists of 3 short data bursts (header), 8 second of alert tones (The old EBS tones), verbal message (max. of 2 min.), and 3 data bursts for the EOM (End of Message).

Each node or relay point in the system has a decoder/encoder that can receive and retransmit the EAS message, including the verbal message. Each entry point has an encoder and possibly a decoder. Entry points with decoder/encoders can and sometimes do become a node or relay point.

The great thing about EAS is now we can utilize the header data, which has an Event Code and Address. If these are not programmed in to the receiver they will be ignored. A message may originate at WSDEM and be addressed to say Chelan County. Even though the message is heard statewide on the network, only equipment in Chelan County will respond.

There are 4 different types of alerts that can occur:

1. National
2. State
3. Local
4. Weather

Washington has set up a VHF relay network that utilizes a Washington State Patrol frequency. This network is controlled from the Washington State Department of Emergency Services building at Camp Murry Washington. The network radiates out from there, using microwave links to all of the State Patrol transmitter sites through out the State. This network gives full state coverage. The decoder/encoder installed at the WSDEM not only can initiate EAS messages, it can also receive them and relay them.

Decoders/Encoders are to be installed at all NWS offices through out the State. In some cases a decoder/encoder is installed right at the NWS transmitter site along with its associated receivers. These units can interrupt the normal NWS program and inject National, State, and Local EAS messages. This makes NOAA/Weather Radio the "All Hazards Radio System" that they advertise. The units installed at the NWS stations have been modified to send the NWS 1050 Hz. alert tone and not the old EBS Alert Tones.

Washington has been broken up into several smaller areas that we call "Local Areas". These may consist of a single county or of several counties combined. In some cases a county may be split where one half is on one area while the other half is in another. Local areas were originally designated by the state plan but may be changed as the local areas and agencies see fit. The State Plan can then be modified to reflect these changes. Each area is expected to have a Local Area Emergency Communications Committee (LAECC) that administers the Local Area. They are expected to set up their own Local Relay Network (LRN). The style and design of this network can vary from one area to another. One area may use the local dogcatcher repeater while another uses a broadcast remote frequency. The better designs use a common repeater site of some sort that can be heard though out the entire area. Each entity that needs to input the system then can transmit up to the repeater and be received by all in the local area. LP1 and LP2 stations are expected to monitor the LRN for their area. NOAA/NWS will also be receiving from the LRN and relaying alerts. This way if an event occurs, the alert can be sent from say the local 911 center to the repeater where it eventually propagates to all Radio, Television and Cable Systems in the area. Individual stations are encouraged to monitor the LRN so they can receive the alerts directly from the source.

If a national alert were sent from our President, It would go directly to KIRO Radio 710 in Seattle, which is the PEP (Primary Entry Point) station for the northwest. Puget Sound stations would receive this alert directly from KIRO. KIRO is also the LP1 (Local Primary #1) station for the Central Puget Sound Area. NOAA/NWS Seattle would also receive it from KIRO and relay it out to all of Western Wash over Weather Radio. It would also be received at WSDEM from KIRO and automatically relayed out on the State Relay Network. Areas that can not hear KIRO directly will get the alert through this path. LP1 and LP2 stations in each area and NOAA/NWS will receive this and relay it to all Broadcasters and Cable Systems. Stations are encouraged to monitor the SRN directly to get the alert as directly as possible.

A second path for this type alert also exists. In this case the National Alert would be received by NPRS (National Public Radio Service), in Washington D.C. where it is relayed up on one of their satellite frequencies. Any NPRS station that has the right equipment can then receive this. KPLU in Tacoma has, and is the LP2 station for the CPS area. This then would also be heard at WSDEM and put out on the SRN. NPRS stations through out the State can receive the same alert directly from NPRS headquarters and transmit it.

The EAS system is such that decoders can handle multiple receptions of the same message yet only retransmit the first one received. This makes for a very redundant system. If KIRO where to fail getting the message, then the KPLU NPRS feed would take over and be received at WSDEM and relayed. If the SRN failed stations could still receive the alert from via their local NPRS station.

If the Governor of Wash. needed to send an alert he would use the facilities at WSDEM and transmit it out on the SRN. This would take the same path as the National Alert through the SRN but would not have the backup of the NPRS. All LP1 and LP2 and NOAA/NWS stations should receive this alert and then relay it. Every Radio, Television, and Cable System should then receive it either from their LP1, LP2 or NOAA/NWS or they could get it directly from the SRN.

Local Alerts would be originated in the County or City Office of Emergency Services or the local 911 center. It would be encoded there with all the parameters and the verbal message would be included. This then would be transmitted out on the LRN where the LP1 and LP2 and NOAA/NWS for that area would receive it. This would then be relayed so all stations and cable systems in the "Local Area" would receive it, either from the LP1 / LP2 or from NOAA/NWS. Stations are encouraged to monitor their LRN so they can receive these alerts directly.

Weather Alerts are originated at NOAA/NWS. These then are sent out on NOAA Weather Radio, which is monitored by all Broadcasters and Cable Systems in the State. The path is then very direct. LP1 and LP2 stations may relay these events as well as the LRN for that area to add redundancy.

The State Plan and its implementation is a work in progress. Broadcasters, State and Local Officials, and NOAA/NWS are working to finish implementation and improve the system. In the past alerts have been initiated both at WSDEM and by Local Areas. The system works very well and is being improved as we complete more of the system.