[SI-LIST] Re: -48v

Dear All,

The high dc voltage was necessary to keep the powdered carbon microphone
capsules happy. Banging them against the table helped, too. Ring voltage
was a completely different phenomena, 90 Vrms/20 Hz, and either centered
around ground or superimposed on the -48 Vdc, depending on the circuit.
If you had a hand-cranked magneto ring generator, life could get even
more exciting; I once measured 1200 Vpp. (BTW, old Army field phones were
great for inducing night crawlers to crawl out of the ground!)

Regards,

Paul
________________

Mahesh Linge wrote:

> Dear Santhosh,
> A large voltage is required to generate a ringing tone in telephone
> system.That's why it is recommended to have a 48 Volts.When phone rings it
> gives atleast 40-45 Volts across the line.
> 
> Regards,
> Mahesh Linge
> ----- Original Message -----
> From: "Santhosh E P" <setavala@xxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Sent: Wednesday, March 24, 2004 11:17 AM
> Subject: [SI-LIST] -48v
> 
> 
> 
>>hi all...
>>is there any specific requirement of having -48v for telephone lines. if
>>then whats the advantage? why we can't have other voltages to carry the
>>signal, not even +ve?
>>regards
>>santhosh
>>
>>
>>------------------------------------------------------------------
>>To unsubscribe from si-list:
>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>
>>or to administer your membership from a web page, go to:
>>http://www.freelists.org/webpage/si-list
>>
>>For help:
>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>
>>List FAQ wiki page is located at:
>>                http://si-list.org/wiki/wiki.pl
>>
>>List technical documents are available at:
>>                http://www.si-list.org
>>
>>List archives are viewable at:
>>http://www.freelists.org/archives/si-list
>>or at our remote archives:
>>http://groups.yahoo.com/group/si-list/messages
>>Old (prior to June 6, 2001) list archives are viewable at:
>>  http://www.qsl.net/wb6tpu
>>
> 
> 
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> 
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
> 
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> 
> List FAQ wiki page is located at:
>                 http://si-list.org/wiki/wiki.pl
> 
> List technical documents are available at:
>                 http://www.si-list.org
> 
> List archives are viewable at:     
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   
> 
> 
> 

-- 
Paul Levin
Senior Principal Engineer
Xyratex Storage Systems

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: