Telephone CO Question
On Fri, 15 Apr 2011 18:34:32 -0700, Jim Thompson
wrote:
On Fri, 15 Apr 2011 17:57:27 -0700, Charlie E.
wrote:
On Fri, 15 Apr 2011 17:48:07 -0700, Jim Thompson
wrote:
Telephone CO Question...
If I suddenly load a short on a telephone line (initial conditions
on-hook)... what is the PEAK current flow that could occur?
Is it the same as the "loop current"?
How is limiting done in a modern CO, series R, or an active circuit?
Thanks!
...Jim Thompson
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Hi jim,
I don't know what they do today, but in the olden days there was a
coil that was activated by that current, so was limited by the coil
(and line) resistance.
In modern CO equipment, they would basically have a active sense
circuit to detect and measure that current. Too little current, and
they determine a line fault condition. Probably too much causes an
alert as well. Since there are multiple customer circuits on a single
line card, I would assume that they basically have a resistor in there
to measure current across, and maybe a relay to cut the line power if
it is out of service...
Charlie
I have sort of a weird line... almost textbook... 50VDC open circuit,
50mA DC when shorted, so a 1K source impedance (or an active circuit).
I going to switch on a "noise maker"... at first jolt, it's simply
just a small valued resistor in series with a zener and a diode.
I don't have any current probes so I was just trying to estimate the
initial surge. I guess just try it while keeping my face covered ?:-)
...Jim Thompson
How far are you from the CO ?
Don't forget to add the miles of copper resistance of the loop.
boB
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