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Developing a 24/7 Digital EAS System

On Aug. 12, I sent my column for the September issue to my editor. Little did I know how soon the Emergency Alert System would come into play, nor the terrible destruction the homeland would soon suffer. After discussions with broadcasters and before Katrina, I started to study the EAS.

It was designed for analog terrestrial transmission systems, which can carry one and only one program at a time. All DTV systems worldwide are packet-based systems that can simultaneously carry multiple datastreams to their intended audiences.

These packets carry a header that identifies what the packet contains--video, audio or data such as an emergency alert. Therefore, DTV instantly can deliver warnings to the public in threatened areas. No other media can do this. Not even the Internet, because who would ever believe it wasn't a hacker's prank or even worse? Broadcasters have the only means to deliver credible emergency alerts to the public and they can do it digitally. Here is how I would go about doing it digitally.


First, the ATSC should incorporate into its terrestrial DTV standard a table of EAS codes for the headers to be transmitted to the public. For example, let every EAS DTV header start with 111. The remainder of each EAS header to be transmitted via DTV defines the nature of the alert and the area affected, for example.

There is also one additional EAS DTV header, a null header. This is the key to a digital EAS. It starts with 111 followed by 000 000--a null packet. It means there is no emergency, hence all those zeros in this header. Broadcasters would transmit this EAS null header continuously in every field. The purpose of the EAS null header is to continuously indicate that the EAS is operational. A broadcaster could monitor their EAS compliance at home.

Consumer electronic manufacturers would design DTV-NTSC downconverters and DTV receivers (appliances) to detect EAS DTV headers. When a DTV appliance detects the EAS null header, a green LED on the front panel lights. This indicates that the station tuned in is part of the EAS, and that the signal is actually being received properly.

If the station goes off-the-air for any reason, that green LED goes off. The appliance is programmed to look for other signals in the locality to see if they are transmitting the EAS null header. If the EAS null header is being received from other local stations, the receiver takes no further action as there is no EAS alert.

Now suppose that the appliance decoded not the EAS null header, but one of the EAS alert headers. The appliance is programmed to determine whether the EAS alert header is on consecutive fields, or perhaps on a majority of consecutive fields.

If so, it tunes the receiver to a second local channel to see if both stations are sending the same EAS alert. If so, it concludes that there is an EAS alert. Now it turns on a flashing red LED visual alarm and a Sonalert, which gives off an audible alarm (like a truck backing up).

Now we have both audible and visual alarms to, if necessary, awaken the household. Would broadcasters ever do that? If, and only if, they are convinced that false alarms will not happen. With the measures I've described; redundant EAS alarms on multiple fields, and on multiple stations, I believe that the only possibility for a false alarm rests with the link from the governmental agencies that originate the EAS alarms and the key broadcasters.


There are presently 34 key broadcasters, from which the remaining broadcasters receive EAS alarms by monitoring two or more of these key stations. I believe there will need to be more key broadcasters--at least three serving the same community. If the federal government cannot protect such messages from hackers and other terrorists, then we've got a much bigger security problem than I care to discuss here.

In the case of DTV/NTSC downconverters, the audible and visual alarms tell households to turn on a radio or TV to receive an emergency message. DTV receivers can activate displays and audio circuits automatically.

Lets talk about awakening people. The small signal electronics needed to tune, demodulate and decode the DTV signal must always be powered up, just as the circuits in modern TV sets respond to commands from a remote control. These are never turned off, just asleep awaiting a wake-up call from the remote control.

Eventually, we may have 250 million such appliances. Each may require 7 watts of power continuously to provide 24/7 EAS monitoring. That power could be cut to milliwatts per appliance if the monitoring circuits are enabled only for a few seconds, say, every three minutes. Electric clocks consume much more power.

This power pulsing would be done in software and random executed so there is no transience on the power grid. However, a battery backup should be provided. If the power grid goes down, families could turn on a battery-powered radio.


Lets talk about the incremental cost to provide this 24/7 EAS monitoring and alarm function. Let's start with the really big-ticket item, the Sonalert. I think these would be 50 cents in quantity to manufacturers. I've bought them at Radio Shack for about $2.50. The two LEDs would be five cents. The software development spread out over 1,000,000 appliances is negligible.

MSTV/NAB have put out a Request for Quote on a DTV/NTSC downconverter. The notion is that if needed, the federal government would subsidize these so that low-income households could still enjoy their free over-the-air TV after the NTSC sunset--tentatively, 2009.

My notion is that the Department of Homeland Security would be much more willing to subsidize the first 10 million downconverters if they got something out of the deal, namely 10 million homes fitted with the world's first 24/7 Emergency Alarm System. That the first 10 million will go to economically hard-pressed people won't hurt either.

That is just the seeding process. While more affluent elements of our populace usually get TV signals via CATV or DBS, those homes have multiple TV appliances that will need a downconverter in 2009, unless they are by then connected to CATV or DBS, which today is the exception, not the rule.

DTV receivers would be more attractive to prospective buyers if they have this 24/7 emergency feature than sets without it, and as you see, even bean counters would see this as an inexpensive feature of their product, especially in the aftermath of Katrina and the prospects of other natural disasters of such proportions.

The West Coast takes Tsunami and earthquake warnings seriously. The entire Midwest knows what tornados or cyclones can do harm quickly, and a manmade disaster may befall a large community anywhere.

If the federal government really wanted to get behind this concept, perhaps receiving appliances with this EAS 24/7 feature would be shipped with a rebate coupon.

That rebate coupon would rebate the sales tax on the purchased appliance. That would lower the cost of EAS 24/7 appliances below that for similar models without the EAS 24/7 feature. Who then would buy the more expensive model without the EAS 24/7 feature? Of course, the Department of Homeland Security would administer and fund this rebate program to stimulate early adoption by the public of this EAS 24/7 warning service.


Looking a little further out, wouldn't it be nice if automobiles were equipped with this EAS 24/7 feature? A lot of people think the world wants to receive DTV in moving automobiles, at least in the back seat. But how about emergency alarm messages where the driver can be warned?

There are people in Korea and Japan already walking about with a personal portable DTV/cell phone appliance. I saw these at the last Consumer Electronics Show. How long before such appliances show up on the streets of New York? Why not warn those pedestrians too?

In fact, to reach these walk-abouts and drive-abouts, why couldn't TV broadcasters carry in their DTV bitstream the digital audio of their own radio stations, and perhap$...? (No that is not a typo, broadcasters might sell some of their data capacity to other radio stations.)

Indeed, when we hear about one-chip DTV receivers, (a slight exaggeration, to be sure), where is the distinction between DTV and digital radio? Such electronic appliances should all have this EAS 24/7 feature. If broadcasters get behind this digital form of the EAS, I predict it will all happen.

Broadcasters will find that meeting their obligation to provide a digital EAS is less costly over their DTV channel than it is with NTSC, and they can expect the digital EAS to be more reliable. What I've described shows how much more effective a well designed DTV EAS would be compared to what we have today.