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Will landline telephones work in a power cut ?

 
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adam2
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PostPosted: Sat Apr 09, 2016 9:45 pm    Post subject: Will landline telephones work in a power cut ? Reply with quote

The accepted wisdom is that they will work.

Various official guides to preparing for emergencies strongly imply that this is the case. Commonplace advice is to have "at least one corded telephone that plugs directly into a BT phone socket"
And warnings that "cordless telephone wont work in a power cut because they need power to the base unit" Which certainly implies that the corded type WILL work.

Historically, basic standard phones definitely worked in a power cut, each phone number had its own pair of copper wires back to the telephone exchange, and had no connection whatsoever with the telephone subscribers mains electricity supply. If indeed the subscriber even HAD electricity, I recall phones working fine in premises with gas lighting and no electricity.

Power to work the phone came from the exchange which was equipped with a very large battery, typically sufficient for 12 hours operation. All but the very smallest exchanges also had a diesel generator, and some important exchanges had duplicated mains supplies as well.

I well recall directly connected telephones in homes or small business working as normal during the rota power cuts of the 1970s.
(many larger companies lacked phone service because they had a private exchange for routing calls to the desired department etc. This equipment needed power and SHOULD have had a backup battery, most had dead batteries)

I do however have considerable doubts as to the reliability of telephones these days in the event of power cuts.
Internet service is increasing supplied by a fibre optic cable to a cabinet in the street, and a relatively short length of copper phone line from the subscriber's premises to this cabinet.
The telephone signal takes the same route.
This equipment needs electricity to function, the fibre optic line back to the exchange simply CAN NOT supply electricity to send a signal down the copper wire.
The electricity is supplied via a standard connection to a street main, like say a street light.
At least some of the cabinets contain a backup battery, but will these work, and for how long ? remember that they probably the cheapest available and are exposed to extremes of temperature.
Note that even if YOUR power is on, that the supply to the street cabinet may fail and interrupt your internet AND PHONE service.

In these days of value engineering, shoddily made imported goods, and general bean counting, I also have much less faith in batteries and generators at exchanges than "back in the day"

Food for thought ?
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clv101
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PostPosted: Sat Apr 09, 2016 10:18 pm    Post subject: Reply with quote

An interesting point. The fibre to the cabinet (FTTC) cabinets do have battery backup for a few hours - though practice might not live up to the theory. However, even when a customer switches to a FTTC Internet connection (like BT Infinity) the copper pair to the exchange is maintained and the voice frequencies still use the copper (and therefore power) back to the exchange.

This is not the case for fibre to the premises customers when there really isn't any copper for voice or data.

Of course the other aspect is mobile phones. Many base station sites don't have any backup power (but some do) so coverage will be greatly reduced in event of a wide spread power cut. However for local power cuts, even covering quite a few miles there's a good chance you'll still see coverage from an unaffected tower.
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biffvernon



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PostPosted: Sat Apr 09, 2016 10:57 pm    Post subject: Reply with quote

Four billion years of evolution have lead to dependency on a dodgy electricity supply. Smile
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PostPosted: Mon Apr 11, 2016 12:03 pm    Post subject: Reply with quote

clv101 wrote:
Of course the other aspect is mobile phones. Many base station sites don't have any backup power (but some do) so coverage will be greatly reduced in event of a wide spread power cut. However for local power cuts, even covering quite a few miles there's a good chance you'll still see coverage from an unaffected tower.


A solar charger or solar-charged batteries for your mobile might be a good idea then.
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Blue Peter



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PostPosted: Mon Apr 11, 2016 4:09 pm    Post subject: Reply with quote

FWIW, I seem to remember that our phones still worked during the powercuts of the 70s,


Peter.
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adam2
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PostPosted: Mon Apr 11, 2016 4:54 pm    Post subject: Reply with quote

Blue Peter wrote:
FWIW, I seem to remember that our phones still worked during the powercuts of the 70s,
Peter.


Yes, they did, but my concern is that with changing technology, especially fibre optic cables, that telephones might NOT work reliably or at all in FUTURE power cuts.
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snow hope



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PostPosted: Mon Apr 11, 2016 5:06 pm    Post subject: Reply with quote

We have fairly regular power cuts and corded phones still work - I keep one specifically for this purpose. Smile I have had FTTC for a couple of years.
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adam2
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PostPosted: Mon Apr 11, 2016 5:14 pm    Post subject: Reply with quote

snow hope wrote:
We have fairly regular power cuts and corded phones still work - I keep one specifically for this purpose. Smile I have had FTTC for a couple of years.


That is somewhat reassuring, thanks for the information.
Anyone else got recent first hand experience ?
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AutomaticEarth



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PostPosted: Mon Apr 11, 2016 9:59 pm    Post subject: Reply with quote

adam2 wrote:
snow hope wrote:
We have fairly regular power cuts and corded phones still work - I keep one specifically for this purpose. Smile I have had FTTC for a couple of years.


That is somewhat reassuring, thanks for the information.
Anyone else got recent first hand experience ?


We had a power cut right across our district last year for about 2 hrs. My parent's place has a corded phone, and when I tried my old corded phone ( I keep one as per Snow Hope above) in my place I had no trouble making a call.
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cubes



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PostPosted: Sat Apr 16, 2016 9:14 am    Post subject: Reply with quote

Don't we also have to hope that the 999 call centre has power or a working backup generator?
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adam2
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PostPosted: Sat Apr 16, 2016 10:09 am    Post subject: Reply with quote

cubes wrote:
Don't we also have to hope that the 999 call centre has power or a working backup generator?


Yes, but no amount of backup power at the 999 call centre will help if your telephone makes use of a fibre optic connection and therefore does not work in a power cut.
Nor will backup power at the call centre help if the power supply at the telephone exchange fails and standby arrangements also fail.
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fuzzy



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PostPosted: Sat Apr 16, 2016 1:22 pm    Post subject: Reply with quote

They could just run exchanges on natural gas powered generators. They would run until the end of BAU.
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RenewableCandy



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PostPosted: Fri May 06, 2016 5:42 pm    Post subject: Reply with quote

The phone exchange here in York got water in it during last year's floods.

I recall the Internet not-working for days, but whether the phones had packed up, I can't remember!

But yes: in the olde days iirc it was 80 volts on the copper wires. It takes a lot more power to ring a phone than to carry and process the speech going down it.
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