I read somewhere that somone was giving away radios to people in areas that might be threatened by earthquakes or tsunami or somesuch but it occurred to me that these radios might actually be switched off during these local or more widespread announcements. of course, the neighbours might raise the alarm or not as the case might be - these households might not have nearby neighbours.

my idea is for the development of a radio that can actually be switched on via an electrical impulse originating at the source of the broadcast either just for the duration of the emergency warning or until switched off manually.
-- po, May 28 2008

Link for [po] http://www.freeplay...PypMCFR8ViQod1CnIhg
Freeplay foundation [Klaatu, May 28 2008]

Stormtracker™ AM/FM Weather Alert Radio & LED Flashlight http://www.hurrican...e.com/product7.html
"This excellent emergency radio helps keep you informed with public broadcasts of all-hazard emergency alerts through The National Oceanic and Atmospheric Administration (NOAA) Weather Radio. By leaving the Stormtracker in alert/lock mode, when an all-hazard emergency or weather alert is broadcast by NOAA, the Stormtracker sounds an audible alert to notify you a message is pending. Depress a button to hear the NOAA report." [phoenix, May 29 2008]

WeatherRadioStore.com http://www.weatherr...hypMCFQGkHgodXxA-iw
A web site with a host of stuff. [phoenix, May 29 2008]

From the NOAA web site http://www.weather.gov/nwr/nwrrcvr.htm
"NOAA Weather Radio All Hazards transmitters broadcast on one of seven VHF frequencies from 162.400 MHz to 162.550 MHz. The broadcasts cannot be heard on a simple AM/FM radio receiver...Prices can vary from $20 to $200, depending on the model. Many receivers have an alarm feature, but some may not...The National Weather Service will send a 1050 Hz tone alarm before most warning and many watch messages are broadcast. The tone will activate all the receivers which are equipped to receive it, even if the audio is turned off. This is especially useful for warnings which occur during the night when most people are asleep." [phoenix, May 29 2008]

How To Cry "Wolf" At 140 Decibels http://en.wikipedia...Civil_defense_siren
[Amos Kito, May 29 2008]

yes, but how? I can see it for EMP pulse ("Danger, increased sunspot activity or we've just been nuked")... would that work for an earth-bound, possibly not in line-of-sight trasmitter ?
-- FlyingToaster, May 28 2008


A device that can be contacted remotely and then alerts its owner could be used for all kinds of communications, especially if most people already carried one. I think we should call it the "pohne", in your honor.
-- jutta, May 28 2008


somehow I read an invisible requirement in the post; that it be unpowered.

You mean a small one-frequency (EBS) receiver very low "standby" power (replace the batteries every few years)? A simple gate (squelch circuit) would do.

I know there's generally emergency frequencies, but do countries have local "public emergency" frequencies? (which would be unused except when they're actually needed)
-- FlyingToaster, May 28 2008


Radio signals themselves can power radios. You have to put up with an earpiece which itself isn't very loud but it is possible.

Perhaps a radio signal could indeed turn on the radio. Even if it didn't draw any standby power from the battery.
-- Bad Jim, May 28 2008


There's a service here in the U.S. that does something like this for weather. I don't see why it couldn't be used for any other emergency information.

I've added a few links.

"I think we should call it the "pohne", in your honor."
There's an idea for you - a protocol to ring and/or deliver a message to multiple phones simultaneously. I'm not sure either the PSTN or cell phone network has the capacity, though.
-- phoenix, May 29 2008


car radios in the UK tend to hike up the volume to ear-drum-bursting level when the travel information comes on - I really despise that.

Not quite sure why I mention that but I just did.
-- po, May 29 2008


The answer is a radio pager, powered by a large lithium-thionyl-chloride primary cell.

A conventional radio pager will run for 60 - 90 days on an AA alkaline battery, which has a capacity of (on average) 2500mAh; some "D" batteries have capacites approaching 20,000 mAh, a factor of 8; one "D" cell woud run a pager mechnanism for about 2 years, and this is off-the-shelf stuff.

With a couple of big LTC cells, getting a mechanism like this to have a standby live of 10 years wouldn't be insurmaountable as the self discharge rate of LTC primary cells is very low.

Add a second set of "action" batteries to power the alarm/receiver and it's quite simple to bake. A small box that stist on a shelf and does nothing for years, untill it receives the paging signal; then it sounds an alarm and activates the receiver.

A battery check circuit would allow you to check battery status by pushing a button, and it could be made to beep like a smoke alarm when the power packs were gettiing low ( >20%). You could even put a smoke alarm in it as well.

If you have an external mains supply - even intermittent - that could extend the shelf life of the device almost indefinitely. Even solar power would help.
-- 8th of 7, May 29 2008


//call it the "pohne", in [po's] honor//
Having a more targeted audience, that's better than an "emergency radio" (although a major disaster will likely affect phone service). But after the first non-useful warning at 3:00AM, I'd leave it turned off. Batteries removed. Circuit board unplugged. Strobe flasher disabled.
-- Amos Kito, May 29 2008


I don't see why battery life is an issue. You replace your smoke detector batteries every 6 months whether they need it or not. How is this any different?
-- phoenix, May 29 2008



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