Which produces most dB/watt; electronic or mechanical?

[Robert Gift]

Sorry to learn abouthe distortion and echoes causing intelligibility problems.

I assume they fully charge the batteries at installation, and solar keeps them topped off so no AC is needed.

Can they NOT be totally independent of AC?

The newspapers and other media should educate the public abouthe
sirens. So easy.

Here, in Yantai, China, they had an article in the Yantai Evening Post
on 8-14 aboutheir ANNUAL test at 09:30 to 10 on 8-15.

[Whelen Rules]

No i am not a Whelen rep. I just like their products. The voice capibility of these sirens are a little better than some but your going to have distortion. Thats the downfall, they worry about making it so loud that the voice is complety distorted unless you talk really slow over pa, and its still distorted. I have heard a Whelen Vortex being used as a PA and it sounds extremly bad. Better off just using tones. I love Whelens tones though especially the "wind up". The 5 second wind down is also pretty cool.

and to answer your question Robert yes they can be fully independent of AC.

[Jim_Ferer]

If a siren runs off batteries during a power outage, the batteries have to be recharged. I've been searching for a sunshne calculator to determine the energy contained in sunshine at different times of the year and at each latitude, but here's an example: This guy is building a solar array with three 4x8 foot solar arrays, and he hopes to get 1600 watts peak out of it.

In Hawaii.

To take a siren off-grid, there could be alternatives. A siren could run off batteries, trickle charged by solar panels. A smart generator system measures the charge in the batteries and turns on the generator long enough to fully recharge the batteries after the siren has rung. We used to have variable message boards at work that worked similarly - the generator ran for maybe three hours a day to charge the batteries.

[Robert Gift]

Would be nice if they had prerecorded (digitally stored) messages
which were cleaned and made super clear and understandable. Perhaps remove much bass which is not important in voice communication. Then, broadcasthe appropriate message. (Like the American woman's voice heard in so many US airports, including Seoul, Korea!)

Would also be nice to have such for our ambulance siren:
"Emergency vehicle. Can you please move right." or
"Emergency vehicle. Can you please stop?"
(Best not to TELL someone. If they do as you order, and have an accident, they may try to sue you - 'He told me to do that!')

This may help with people who do not knowhat to do and not panic them as a siren may do. And also not concern patients who worry when they hear the siren used for themselves.

[Robert Gift]

If a siren runs off batteries during a power outage, the batteries have to be recharged. I've been searching for a sunshne calculator to determine the energy contained in sunshine at different times of the year and at each latitude, but here's an example: This guy is building a solar array with three 4x8 foot solar arrays, and he hopes to get 1600 watts peak out of it.

In Hawaii.

I hope he has enough sunny days where he is located.
What would 4x8' solar cells cost?
And maybe hook up a bicycle to a generator for exercise
and charging! http://www.lksos.com has a bicycle-powered siren!

To take a siren off-grid, there could be alternatives. A siren could run off batteries, trickle charged by solar panels. A smart generator system measures the charge in the batteries and turns on the generator long enough to fully recharge the batteries after the siren has rung. We used to have variable message boards at work that worked similarly - the generator ran for maybe three hours a day to charge the batteries.

With LEDs do the generators need to run as long? Or can they be completely run from solar cells?

If we have a stormy day inwhich a tornado warning is sounded and drains the batteries, and continued stormy days, as is often the case,
then the batteries may not gain enough charge for another warning.

[Jim_Ferer]

Robert: "With LEDs do the generators need to run as long? Or can they be completely run from solar cells?

You're right; that's why we "used" to have them. Most VMSs use flip disks, which are magnetically actuated disks that flip from a black side to a reflectively painted side, with a light in the middle of each disk.

Now there are plenty of pure LED VMS signs, and these are generally entirely powered by solar-charged batteries. 100 percent LED technology dramatically reduces current demands. The LEDs, the control module, and the cell phone are the only parts that draw anything at all. Even so, we've occasionally had to take a generator out and recharge a sign in the winter or after several days of dark skies. (This is in and around NYC)

The thing about a siren is that it goes for weeks or months doing nothing and then draws high amounts of power for a few minutes at a time. Solar cells wouldn't be able to recharge the batteries easily. You'd have to get them recharged faster. The controls and SCADA system don't draw a lot.

[Robert Gift]

What is VMS?
Vehicle -?- Sign ?

I'm surprised LED technology hasn't yet progressed into household
lighting.
I've been waiting for years.
Will be so nice to have lower energy bills and far less heat than from even compact fluorescent lights.

What is the hold-up?

[Jim_Ferer]

Variable Message Signs are those displays by the side of the road or on a sign structure that say "New Traffic Pattern Ahead" or "Click It or Ticket" or whatever.

LEDs stil don't generate as much light per watt as flourescents do, and there's the cost factor as well. White LEDs are still hard to make, but the state of the art is changing fast and improvements are coming along every month. The day will come. LEDs are being developed for laptop backlighting that will improve batter life and color on laptop screens.

There's a lot being done.

[Robert Gift]

Interesting. I thought LEDs were MORE lumens/watt.
Nichola Tesla still deserves credit for his developement of the fluorescent light.

I've always wanted to hack into a VMS and change the message.
I've never seen those magnetic flip disks with a light in them.

Thanks,

[Jim_Ferer]

I'll bet you have seen flip disks without realizing it; they're very common. If you see a lot of green in the letters it's almost surely a flip disk.

Most portable VMSs have a cell phone in them, at least in or around NYC.

Without people like Tesla, there would be no progress. We stand tall because we stand on the shoulders of giants. Any other attitude would be like putting down Thomas Edison for not coming up with LEDs.