[Asterisk-Users] Line Override Device

[Steven Critchfield]

On Sun, 2003-07-13 at 15:55, John Laur wrote:
> > You can build a UPS for that, but the better option here is to attach
> a
> > phone to the phone side of the X100P that is always connected to the
> > POTS line so that even when the computer goes down you can send and
> > receive calls.
> 
> If you don't want it to ring *unless* the power is out, you could wire
> it through a normally-closed relay hooked to something simple like the
> parallel port (there are schematics everywhere for this). When the
> computer is off, the relay closes, and the phone rings with the line.
> Heck, if you have an analog set on FXS you want to ring when power goes,
> you could get a SPDT relay and wire one line into open and one line into
> closed and switch between them. If you don't care much about incoming
> calls during the outage, just plugging a phone into the other end of
> X100p and turning off the ringer will do the trick.

It is easier to wire to a 12 volt(yellow) wire off of the PSU, plus this
lets you drive larger relays.

> > The specs are available on the net to show you how to wire POE (Power
> > over ethernet). In fact I did my own so I can use the 7960 before we
> > found a suitable wall wart. Basicaly all I did was punch down a
> keystone
> > with the ethernet data lines, then punched down the power lines so
> that
> > one side had power and the other didn't so I didn't chance blowing up
> my
> > switch that was made before they thought of doing POE. I used the
> power
> > supply from a CAC AB1 that had the ringer module broke on it. It
> > produces 1amp of 48volts and was more than adequate for the 7960. If I
> > had a lot of phones to power, I have a 6amp 48volt PSU from a Premisys
> > channel bank that I picked up at a hamfest for $10.
> 
> If you do this and plug anything other than the 7960 into it like a NIC
> you can easily damage it! (google for 'etherkiller' for more) Real power
> over ethernet injectors provide power only to devices that 'ask' for it,
> but for small setups they are very much more expensive than the price of
> a UPS that could power the 7960 for hours (a $30 ups running only the
> 7960 should go for at least a couple hours) - Compare this to paying
> $100+ per port for PoE injectors! Putting 'raw' 48V on the Ethernet in
> an office environment where someone else might accidentally plug
> something into the wall jack incorrectly would be a disaster! Of course
> there are some cost savings associated with not having to maintain and
> upkeep 48 UPS's for 48 phones that make PoE worth it, but I'd say that
> for less than 12 users it becomes harder to justify.

etherkillers are 110 volts AC to data pins, POE is 48 volts DC on non
data pins. This should not blow devices that are not expecting PoE.
Think about it, how would a device ask for power if it doesn't have
power to make the request?  


-- 
Steven Critchfield <critch at basesys.com>