Fire trucks, ambulances, and police cars should have the ability to broadcast low-power sirens on all FM and AM radio frequencies. That way, even if some idiot is listening to the radio too loudly, s/he will still know that an ambulance is coming. This obviously wouldn't effect CD or tape playing, but it would make things a little safer.
-- simpleknight, Nov 13 2000

CreativeLtg's link as a link http://www.creativelight.com
This is the place to put it, CreativeLtg. [neelandan, Mar 15 2002, last modified Oct 04 2004]

RBDS http://en.wikipedia...i/Radio_Data_System
It's got this very feature. Too bad no one knows about it. [Acme, Jul 28 2005]

Emergency Car Radio Car_20radio
An identical, but belated idea [Acme, Jul 28 2005]

Wouldn't this muck up the doppler shift that enables us to tell *where* that ambulance is coming from?
-- imagooAJ, Nov 13 2000


[sp: affect. "effect"=cause; "affect"=change.]

The complaint about loss of directionality is correct, but the doppler shift part of the signal distortion only tells us whether it's headed our way or away from us, not where it is.

(Of course, in an inner city, sound bouncing off walls makes it hard to tell where something is coming from to begin with.)
-- jutta, Nov 13 2000


When you hear a siren now, you automatically reach for the radio volume to turn it down so you can hear better, in order to "find" the source. With the radio broadcast you would behave no differently, turn down the sound of the siren on your radio in order to better hear the real thing.
-- blahginger, Nov 14 2000


Right, but I have found that often I don't hear the siren until it is almost on top of me, but if I didn't have the radio on, I would have heard it much sooner. I imagine that there are many folks who have their radio on louder than I do.
-- simpleknight, Nov 14 2000


But, the transmitter's power would have to drop off pretty quickly after a certain distance, especially on the am stations. Otherwise, everyone within the same county as the ambulance will hear it, and there would be nothing but ambulance siren 24/7. Also, what about stationary radios, like those in houses, which shouldn't have to pick up the siren broadcast?
-- nick_n_uit, Nov 14 2000


Perhaps the car could hear the siren for you. A small mike on the outside of the car could pick-up on the siren sound and activate a flashing light on the dash or possibly a corner of the windscreen, turning the ineffective sound into an effective visual warning.
-- DrBob, Nov 14 2000


I've seen a proposal for something like DrBob's idea in an old Popular Mechanics. A little light on the dashboard that would light up when a cop or ambulance near.
-- StarChaser, Nov 16 2000


Don't certain radar detectors also detect "Emergency Vehicle Signals" (not sure of real name) ? I'm pretty sure I saw a line of these devices that could pick up a signal from any emergency vehicle (Cop, Fire, Ambulance, Highway dept. vehicles, etc.) when the you(they) came within a certain distance of them(you).
-- bosco, Nov 16 2000


I cant find the link now, but my Kenwood car stereo system had (this was about 2 yrs ago) a menu option that, when set to "on", would overide the current music settings with a loud beeping signal if there was a siren in the near vicinity. I dont know how it worked, but it saved me from being in the way of an ambulance once. It shut down the CD player and beeped at me, showing "ALARM" in the display panel.
-- ickledinkle, Jan 11 2001


Interesting - I have been working on this since 1993. We are currently developing the transmitter for ambulances (and fire etc). It uses the RDS (Radio Data System) and a specific frequency. A 'blanket' approach won't work in a practical sense - what if you were listening to a cd or tape with the volume up? Our system will switch you over and to the transmission automatically - even if you had your radio switched off - for the duration of the broadcast being in range. The transmission will also be accompanied by text (for stereos with alpha numeric displays) telling you its fire or ambulance or police etc. In the future, this will include map info ("ambulance on x highway travelling north" for example. My company info is at www.creativelight.com, though we arent releasing info ont he system (RDS-ESP) until later in the year.
-- CreativeLtg, Mar 15 2002


My company looked at doing a quote for an ERDS system; I think we no-bid it since there wasn't really enough in the specifications to accurately tell what was required.

The biggest limitation I saw in the ERDS proposals was the use of a single frequency; since the system relied on voice transmission to give drivers the actual warning message, it was not possible to time-multiplex different transmissions effectively, and thus there was no way to provide adequate warning to everyone in the vicinity of multiple vehicles, even if the vehicles know of each others' presence.

Otherwise, I'm curious how you resolve the issue of where the signal is coming from. My personal recommendation would be to equip emergency vehicles with a number of directional antennas and a compass. Any compass-equipped receiver would thus be able to identify where an emergency vehicle was in relationship to itself without needing a directional antenna itself.
-- supercat, Mar 15 2002


I've mentioned this idea to people - nobody seemed to like it, as it appears to open up the ability for others to toy with our broadcasts. I must admit, I could easily see all kinds of other uses coming into play as soon as the technology is established. Police could actually address you via radio to pull over; drivers could tell each other when they see a gas flap (or their car's fly, as I like to call it) open (or tell each other to go F**k themselves after getting cut off); and of course, the amateur lunatics will go around distracting others with outrigh silliness just because they figured it out.

Anyway, I do wish more intersections were equipped with the warning light for siren vehicles approaching. Visual cues work better in a car, even with loud music on.
-- XSarenkaX, May 31 2002


I have a hard time noticing the siren even with the radio off. Often the first clue I have that an emergency vehicle is in the area is that I notice other people pulling over.

XSarenkaX, take a look at some of the other halfbakery car communication ideas --- mostly in the "Car: License Plate" category, but also "Car: Communication", etc.
-- wiml, May 31 2002


Regarding the distance issue, it can certainly be made directional and broadcast it only in front of the emergency vehicle. Perhaps car horns can have this feature as well.
-- Worldgineer, Jul 27 2005


There is always the killjoy philosophy that you ought also to be able to hear car horns or the sound of pedestrians as they ricochet off the bonnet, as well as sirens. I never understood why mobile phones are thought to be more distracting than over-loud music.
-- Basepair, Jul 27 2005


Studies seem to indicate it's attention that's the issue. Talking on a cell phone requires more attention than listening to music - but then so does talking to passengers.
-- Worldgineer, Jul 28 2005



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