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Ismael Gil

2014-Jul-10 10:40 UTC

[asterisk-users] Digium E1 card stops working til disconnect machine power cord

<html><head></head><body><div
style="font-family: Verdana;font-size: 12.0px;"><div><span
id="result_box" lang="en"><span
class="hps">Hi
there</span><span>,</span><br/>
<br/>
<span class="hps">In one of my</span> <span
class="hps">asterisk</span> <span
class="hps">installation,</span> <span
class="hps">there is a</span> <span
class="hps">Digium</span> <span
class="hps">E1</span> <span
class="hps">pri</span> <span
class="hps">card</span> <span
class="hps">connected</span><span>.</span><br/>
<span class="hps">The</span> <span
class="hps">asterisk</span> <span
class="hps">and card</span> <span
class="hps">are</span> <span
class="hps">working properly.</span><br/>
<span class="hps">The problem</span> <span
class="hps">we have is that</span> <span
class="hps">when a storm</span> <span
class="hps">occurs in the area</span><span>, the
card</span> <span class="hps">stops working,</span>
<span class="hps">and</span> <span
class="hps">E1</span> <span
class="hps">lines</span> <span
class="hps">connected</span> <span
class="hps">not rise</span><span>, even</span>
<span class="hps">restart</span> <span
class="hps">the machine.</span><br/>
<span class="hps">If</span> <span
class="hps">however</span> <span
class="hps">if you turn off</span> <span
class="hps">the machine,</span> <span
class="hps">disconnect</span> <span
class="hps">the power cord</span><span>,</span>
<span class="hps">reattach it</span> <span
class="hps">and</span> <span class="hps">turn
on the</span> <span class="hps">machine
again</span><span>,</span> <span
class="hps">E1</span> <span
class="hps">pri</span> <span
class="hps">card</span> <span
class="hps">correctly</span> <span
class="hps">recognizes the</span> <span
class="hps">E1</span> <span class="hps">lines
and</span> <span class="hps">the PBX</span> <span
class="hps">starts to</span> <span
class="hps">function properly.</span><br/>
<span class="hps">This only happens</span> <span
class="hps">when there are</span> <span
class="hps">storms in the
area</span><span>.</span><br/>
<br/>
<span class="hps">Why is it</span> <span
class="hps">necessary to disconnect</span> <span
class="hps">the power cord</span> <span
class="hps">for</span> <span class="hps">the
card to work</span> <span class="hps">after a
storm</span><span>?</span><br/>
<span class="hps">How</span> <span
class="hps">I can</span> <span
class="hps">identify</span> <span
class="hps">where the problem
is</span><span>?</span><br/>
<span class="hps">How</span> <span
class="hps">I can</span> <span
class="hps">fix it?</span><br/>
<br/>
<span class="hps">Thanks in</span> <span
class="hps">advance</span><span>,</span><br/>
<br/>
<span
class="hps">Ismaeleitor</span><span>.</span></span></div></div></body></html>

A J Stiles

2014-Jul-10 12:31 UTC

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[asterisk-users] Digium E1 card stops working til disconnect machine power cord

On Thursday 10 Jul 2014, Ismael Gil wrote:> Hi there,
> 
>  In one of my asterisk installation, there is a Digium E1 pri card
> connected. The asterisk and card are working properly.
>  The problem we have is that when a storm occurs in the area, the card
> stops working, and E1 lines connected not rise, even restart the machine.
> If however if you turn off the machine, disconnect the power cord,
> reattach it and turn on the machine again, E1 pri card correctly
> recognizes the E1 lines and the PBX starts to function properly. This only
> happens when there are storms in the area.
> 
>  Why is it necessary to disconnect the power cord for the card to work
> after a storm? How I can identify where the problem is?
>  How I can fix it?
> 
>  Thanks in advance,
> 
>  Ismaeleitor
It's a phenomenon called "latch-up", which occurs when extreme
voltages are
applied to the inputs of CMOS logic ICs.

A parasitic PNPN structure -- which is unavoidably present at each pin -- 
ordinarily provides some measure of static protection, by acting as diodes to 
clamp the voltage on any pin to the power rails; but it can also act like a 
PNP and NPN transistor in a sort of deadly embrace, where each one is holding 
the other in conduction.

If enough current flows into or out of an input pin under fault conditions, one 
of these transistors can turn on, which will cause the other transistor also 
to turn on; and the input can become clamped hard against one or other power 
rail.  This situation will persist as long as any current is flowing through 
the transistors, which in practice means until the supply is disconnected  
(or, in extremis, until the device overheats and melts down).

See also Wikipedia article: http://en.wikipedia.org/wiki/Latchup

-- 
AJS

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