Phil:
This nails it down as destined for a telco supply. Yes, Phil, the polarity
switch is
all that is required. Marlin P Jones has one -48 VDC 1 amp (roughly 48
watts)
for $56, and one used -48 VDC 15 amps (roughly 750 watts) for $40.
A little history: telephone companies use/used batteries to supply their
power
to the lines. Whether it is +48 VDC or -48 VDC depends simply on whether the
positive or negative supply line is attached to the ground (yes, to the
earth itself).
In modern supplies directly attached to the device both lines are attached,
and
neither line goes to ground, so a simple polarity switch is all that is
required.
-48 VDC is the nominal line voltage on a telephone system. This drops to
about
-20 VDC when someone picks up a receiver. The ringing voltage is about
90 Volts AC, which can easily damage sensitive DC based equipment, and
cause interference on adjacent data lines.
I am surprised at the wattage requirement. The 9 volt battery scheme
wouldn't
supply enough amps, and the 6 volt battery scheme would run the batteries
down pretty darn quick.
-----Original Message-----
From: Circusnuts [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, July 11, 2000 4:49 AM
To: Ray Mosely
Subject: Re: Running a DC powered Catalyst 1900 ???
Hey Ray- this is great information, but I have revisited the specs for this
switch...
http://www.cisco.com/univercd/cc/td/doc/product/lan/28201900/1900dc/dcpwrint
.htm#xtocid231323
To add to the mix, this requires: 39W, -40 to -60 VDC
Any ideas- could this be done with a polarity change ???
Thanks !!!
Phil
----- Original Message -----
From: Ray Mosely
To: Circusnuts ; [EMAIL PROTECTED]
Sent: Monday, July 10, 2000 2:30 PM
Subject: RE: Running a DC powered Catalyst 1900 ???
Somebody else said that it was 48 volts.
That's the line voltage on a telephone line, and
as we know, a telephone line does not carry a
lot of amps, so almost any 48 volt source would be
enough.
Two marine batteries, or four garden tractor batteries
would carry it for many days before needing re-charging.
You could hook up 8 of those big square 6 volt batteries.
5 or 6 9-volt batteries would probably run it, but they would
poop out pretty quickly.
The best bet is to find a telco supply, like Marlin P. Jones,
and order a 48 volt power supply.
http:/www.mpja.com
Their catalog lists 48 volt supplies starting at $4.00 and up.
Good luck,
Ray M,
CCNA
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Circusnuts
Sent: Thursday, July 06, 2000 8:05 PM
To: [EMAIL PROTECTED]
Subject: Running a DC powered Catalyst 1900 ???
I think I've goofed. I bought a Catalyst switch & did not read the ad
correctly. I have a DC running device. How can I use this ???
Any advice (other than jumper cables from my car :-)
Thanks !!!
Phil
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