On 17/11/2011 3:50 p.m., Robert Cooze wrote:
> On 17/11/11 16:07, Bruce Sinclair wrote:
>> In article<ja1ie6$mc5$>,
>> "~misfit~"<> wrote:
>>> Somewhere on teh intarwebs bugalugs wrote:
>>>> On 16/11/2011 10:06 p.m., Frank Williams wrote:
>>>>> On Wed, 16 Nov 2011 18:45:13 +1300, bugalugs<>
>>>>> wrote:
>>>>>> On 16/11/2011 2:49 p.m., Frank Williams wrote:
>>>>>>> On Tue, 15 Nov 2011 19:01:53 +1300, (Your
>>>>>>> Name) wrote:
>>>>>>>> In article<j9sjjp$qpc$>,
>>>>>>>> victor<> wrote:
>>>>>> <snip>
>>>>>>> Total rubbish as some time back we had a power cut and we lost our
>>>>>>> Analogue Phone due to the fact that some one at the exchange had
>>>>>>> forgot to check the batteries.
>>>>>>
>>>>>> Couldn't they just duck down to Dick Smith and get a couple ???
>>>>>
>>>>> Do they sell 50v Batteries..?
>>>>
>>>> They could string some together. Wouldn't the exchange do that?
>>>
>>> Of course they do, as there's no such thing as a 50V cell (TTBOMK) it
>>> stands
>>> to reason that a 50V source would be a 'battery' of cells. 
>>
>> I recall when at school (a long time ago now), there was an old 1.5 V
>> battery supposedly surplus from the phone exchange. It was a lead acid
>> battery, about a foot square and almost 3 foot high (that's about 30 x
>> 30 cm
>> and perhaps 50 cm high for the younguns
). It was 10 A. 
>>
>> The answer to the question on everyone's lips (what happens if you put a
>> screw driver across those large screw terminals
), is ...
>>
>> it welds itself to the terminals and has to be kicked off.

>> Yes, a chuck of screw driver flew off in a random direction too. 
>>
>>
>>
> The memory's I started life in the post office (Telecom) There was a
> room full of those cells two rows of them both banks 50 volts each.
> there was some very large copper bars running the length of the
> exchange. anything metal was said to vaporise if shorted across the +
> and - Rail there was a also a large rectifier room where the mains from
> out side was turned into DC 50V. last but not least there was a big
> Diesel generator for when the mains went out. although the voltage was
> low the amperage was in the 1000's of amps
Most exchanges and communication installations were set up like that.
Most had batteries large enough to run the exchange for some hours after
which the diesel generator would cut in. There was usually enough diesel
stored to run the exchange for a couple of weeks. (microwave
installations which could be snowed in) In some exchanges the Mains
powered a large electric motor which drove a ton or so of flywheel.
When voltage dropped, or failed the diesel would fire up and drive the
flywheel which would then drive the electric motor which would then
become a generator.
--
Everyone is entitled to be stupid, but some abuse the privilege.