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
\
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