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Home > Archive > Emergency services > May 2005 > Re: When You Dial 911, Can Help Find You?
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Re: When You Dial 911, Can Help Find You?
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| Don S wrote:
> In article <3d71919alco4nhjicgdh37atfldcoeu8sa@4ax.com>, moc.enilepip@ykkams wrote:
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>
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> Sorry, in my earlier comments, I thought you were referring to a building with
> a MTSO/CO/cell site. The Outside Plant Cabinets do have self contained HVAC
> units. Usually, only critical locations have a gen-set.
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> The cabinet contains power and batteries, usually in the form of
> "mono-blocks". These are similar to a car battery, in that each unit contains
> 6 * 2V cells, for 12V. The rule of thumb is to provision for 8 hours
> backup, but actual run time may be much less. As you noted, if it gets too
> hot in the cabinet, the radio/telecom gear will shut down before the batteries
> die.
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> Those are called wet cells. Valve Regulated Lead Acid (VRLA) batteries were
> introduced as a "maintenance free" alternative to wet cells. They use a gel
> instead of the water. Unfortunately, they have proved to have a much shorter
> life span (~5 to 7 years) vs the 20+ years you can get out of a properly
> maintained set of wet cells.
>
All true, but the maintenance-free nature of the newer gel-cell batts,
despite the shorter life spans, are thermally more stable, occupy less
space and can be recycled. VRLA batts require regular hands-on
maintenance, are comparatively huge, and cost more to dispose of even
after their longer-term life.
--
jer
email reply - I am not a 'ten'
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