[Asterisk-Users] Line Override Device

[John Laur]

> 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.


> 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.

> BTW, for the UPS, we have some powerware UPSs that have plugs for
> external batteries. In our former server room we have one with 5 car
> battery sized batteries attached to it. We feel we had about a 10 hour
> run time.

Even a lot of the UPS's that don't have plugs for this stuff can still
be run with external batteries if they have a good charge controller
that can deal with it. I have seen a lot of weird setups that use car
and tractor batteries glommed into APC ups's that run lots of important
systems! Go for it if you can justify the risk.. 

John