From what I recall and understand, the **EBS ** was a government phone tree if you will. The word for a national emergency would go out to about 40 or 50 primary stations. These signals would in theory be picked up by dozens more stations each and etc. until the entire nations Radio and TV system was ready for Emergency information and/or a Presidential address.
The Test was actually for the secondary or perhaps tertiary stations to see if the got the signal. The Beeps I could only wag were some form of coded message to these stations.
This is pretty hazy information, I learned back around 1982 or 83 so excuse me for some mistakes when a expert shows up.
Okay, but why the weird sounds. Or, more exactly, do these sounds have some kind of effect on other stations? If so, how? From your explanation, What Exit?, the station that does the test is trying to send a signal to other stations. If this signal is for other radio stations, why bother to have regular listeners hear them?
It wasn’t needed (except possibely in NYC & DC). Conventional news channels where able to broadcast quite effectively. Indeed most non-children’s channels either shutdown or switched to a feed of whatever their corporate owner’s news channel was. C-SPAN even broadcasted CBC Newsworld for some reason.
I am really out of my depth, but the beeps were a code that told the stations if it was a test, a disaster, war, Imminent nuclear attack, etc. I believe the receiving stations were suppose to break out the pertinent regs to tell them what to do. The idea was that this was a method of communications that is not reliant on other means. Similar to the reason Darpanet was developed. The US wanted to use multiple technologies to have redundant methods of communications.
You lived within the broadcasting range of either a primary or secondary station is my guess. I recall WNEW, channel 5 in NYC was a primary station.
The tones are part of a system called Specific Area Message Encoding, and they encode various bits of information such as who authorized the alert, what region it’s intended for, and the nature of the alert, among other items.
The reason you hear the tests is because you are supposed to hear them. EAS equipment is supposed to be able to cut into the broadcast signal; the test fails if it doesn’t cut in. The equipment generates a printout with the specifics of the test, such as the station sending the alert, the nature of the alert, and the stations downstream, as it were, who are getting the alert from your station. If the test fails, the printout will show that, and the engineer gets a phone call. That printout is required to be entered into the station’s official log.
anyrose, the EAS wasn’t even activated on 9/11. So many broadcasters, both TV and radio, had transmitters on the roof of the WTC that there wouldn’t be any point to activating it. There is a certain amount of redundancy built in to the system, but it’s hard to plan for massive destruction of the physical infrastructure. The same happened during and after Katrina.
The original Emergency Broadcasting System* was a system where a station would drop it’s carrier several times, then transmit a 1000 hz tone to alert listening stations that there was an emergency. This was later found to be impractical, so it was changed to have a station transmit two tones simultaneously, a mix of 853 Hz and 960 Hz tones for between 20-25 seconds. The tones would trigger receivers in other stations that were required to listen to them, and it was followed by a message - usually a test, sometimes a civil defense message. It was basically a big government phone tree.
It has now been superseded by the Emergency Alert system. This is what you hear today, with the brazzy tones going BRaaaaP BRaaap! Those tones are a digitally encoded message that trigger receivers in listening stations and print out the message sent. The advantage is that the tones can be sent over a program - you don’t have to stop programming to send them.
Back when I was in broadcasting, the alert notification system at my station was tuned to the primary station. When the primary station broadcast the emergency tone (the first of a succession of weird sounds) it triggered the system, which sent up a gawdawful racket that we could hear all over the station. At that point, we listened to the emergency signal off the air to determine whether it was a test or a real emergency.
Later on, the signal became digital instead of analog, but I think the principle still remains:
It has to be broadcast on the normal frequency. After all, if the public doesn’t hear it, it’s not effective.
It has to be broadcast at a certain length and volume so random, similar signals don’t trip the equipment.
Similarly, my station had to broadcast a test so we could verify the equipment was working (at least on our end.)
As for what indicates a failed test, if Station A records that they sent the signal at X time, and Station B doesn’t record they received it, that indicates a failed test.
The networks and news services were also part of the system, and they usually did their tests when they weren’t sending live programming. But a radio or TV station has to be broadcasting all the time it’s on the air.
Well, normally these “tests” are just some kind of weird sounds. But a week ago, they had the sounds, and a voice that talked about what we would be told to do in an emergency. Then, back to regular programming. But it has happened only once.
Broadcasters aren’t required to transmit a spoken message for the required weekly tests, although they are for required monthly tests. What you probably heard was a required monthly test.
The system has undergone changes over the past few years to take new technologies like satellite radio and television and digital cable into consideration.
Also, I stand corrected on the EAS non-activation on 9/11. It turns out that WCBS-TV had alternate transmission equipment on the Empire State Building and shared time with the other TV stations in the area until other arrangements could be made. It has also been argued that the immediacy and depth of media coverage of the disasters was so total that the EAS wasn’t necessary. (See here, here for more information.)