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mfdutra at gmail.com
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 Posted: Fri Apr 11, 2008 9:43 pm Post subject: [asterisk-users] X100M never goes on-hook state |
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Hi guys,
I've been experiencing a very strange issue with my Digium Card TDM400
as of this week. It has two FXS and two FXO.
The FXO modules (both of them) never goes on-hook after hanging up in
Asterisk. It had worked perfectly well for over four years.
I put an ammeter in series with the line and the card, and immediately
after plugging the connector to the card, I got 26mA in the circuit and
a dial tone from the carrier, where it should be zero amper (on-hook
state). If a Dial() something, it works perfectly. I can Hangup() the
call, freeing the channel in Asterisk, but the hardware keeps off-hook
forever, locking the line. If I Dial() again, Asterisk opens the line,
sends the DTMFs normally, but it doesn't work since the carrier thinks
I'm still holding the first call.
It behaves exactly the same way with another analog line. If I plug
either of the lines and my other Digium card (TDM2400), it works ok. The
same with my Brazilian DigiVoice FXO card.
Ok, you all might say: your card is damaged, throw it away. Ok, I could
do it, but now comes the funny part:
If I put an DSL filter in series with the line and the card, IT WORKS
PERFECTLY!!! The filter imposes 25 ohms over the circuit. Maybe that's
causing the card to work. When I put the filter and the ammeter in
series, I get zero amper when on-hook and 26 mA when off-hook, that's
the expected behaviour.
I'm not an expert in electricity, so I really don't know why the card is
behaving that way. What does that resistance make for the card to start
working ok? I know the DSL filter isn't only a resistor. Maybe it has
another electrical component that's helping more than the resistor. Just
a guess.
Tomorrow I'll buy a 30-ohm resistor, take the DSL filter off, and test
the card only with the resistor, to check it out.
In order to isolate the problem even more, I plugged the FXO port in one
FXS port. Immediately after plugging it, Asterisk announced at the
console that someone went off-hook at the FXS port. So, it's not really
a carrier issue. The FXS port is perfectly -48V on-hook, and about
20 mA in the circuit when off-hook, closer than the carrier to the
standard values.
Any clue is welcome.
--
MARLON DUTRA
Propus
GnuPG ID: 0x3E2060AC pgp.mit.edu
http://www.propus.com.br/
http://hackers.propus.com.br/~marlon/ |
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novackster at gmail.com
Guest
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| Posted: Sun Apr 13, 2008 11:15 am Post subject: [asterisk-users] X100M never goes on-hook state |
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You need to replace the FXO module
Was there ever any sort of protection installed for the module?
Not what your carrier provides, that protects their equipment, but any
secondary protection?
These modules are easily damaged. I know of one connected to a very old
SXS switch that damages from a small inductive kick when it opens ( goes
on hook )
John Novack
Marlon Dutra wrote:
| Quote: | Hi guys,
I've been experiencing a very strange issue with my Digium Card TDM400
as of this week. It has two FXS and two FXO.
The FXO modules (both of them) never goes on-hook after hanging up in
Asterisk. It had worked perfectly well for over four years.
I put an ammeter in series with the line and the card, and immediately
after plugging the connector to the card, I got 26mA in the circuit and
a dial tone from the carrier, where it should be zero amper (on-hook
state). If a Dial() something, it works perfectly. I can Hangup() the
call, freeing the channel in Asterisk, but the hardware keeps off-hook
forever, locking the line. If I Dial() again, Asterisk opens the line,
sends the DTMFs normally, but it doesn't work since the carrier thinks
I'm still holding the first call.
It behaves exactly the same way with another analog line. If I plug
either of the lines and my other Digium card (TDM2400), it works ok. The
same with my Brazilian DigiVoice FXO card.
Ok, you all might say: your card is damaged, throw it away. Ok, I could
do it, but now comes the funny part:
If I put an DSL filter in series with the line and the card, IT WORKS
PERFECTLY!!! The filter imposes 25 ohms over the circuit. Maybe that's
causing the card to work. When I put the filter and the ammeter in
series, I get zero amper when on-hook and 26 mA when off-hook, that's
the expected behaviour.
I'm not an expert in electricity, so I really don't know why the card is
behaving that way. What does that resistance make for the card to start
working ok? I know the DSL filter isn't only a resistor. Maybe it has
another electrical component that's helping more than the resistor. Just
a guess.
Tomorrow I'll buy a 30-ohm resistor, take the DSL filter off, and test
the card only with the resistor, to check it out.
In order to isolate the problem even more, I plugged the FXO port in one
FXS port. Immediately after plugging it, Asterisk announced at the
console that someone went off-hook at the FXS port. So, it's not really
a carrier issue. The FXS port is perfectly -48V on-hook, and about
20 mA in the circuit when off-hook, closer than the carrier to the
standard values.
Any clue is welcome.
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Dog is my co-pilot |
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jra at baylink.com
Guest
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| Posted: Mon Apr 14, 2008 8:30 am Post subject: [asterisk-users] X100M never goes on-hook state |
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On Fri, Apr 11, 2008 at 11:43:19PM -0300, Marlon Dutra wrote:
| Quote: | If I put an DSL filter in series with the line and the card, IT WORKS
PERFECTLY!!! The filter imposes 25 ohms over the circuit. Maybe that's
causing the card to work. When I put the filter and the ammeter in
series, I get zero amper when on-hook and 26 mA when off-hook, that's
the expected behaviour.
|
It's possible the 'line relay' on that card is not a physical relay,
but electronic, and that its sensitive to too much loop current -- and
the DSL filter drops the current far enough for that 'relay' not to
pull in spuriously.
Telecom guy Mike Sandman has a paper on loop current on his website:
http://sandman.com/loopcur.html
and, come to that, lots of *really* cool stuff for sale as well; if
you've never looked at his site, do.
Cheers,
-- jra
--
Jay R. Ashworth Baylink jra at baylink.com
Designer The Things I Think RFC 2100
Ashworth & Associates http://baylink.pitas.com '87 e24
St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274
Those who cast the vote decide nothing.
Those who count the vote decide everything.
-- (Joseph Stalin) |
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mfdutra at gmail.com
Guest
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| Posted: Mon Apr 14, 2008 12:06 pm Post subject: [asterisk-users] X100M never goes on-hook state |
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Hello,
On Mon, Apr 14, 2008 at 10:30 AM, Jay R. Ashworth <jra at baylink.com> wrote:
| Quote: | It's possible the 'line relay' on that card is not a physical relay,
but electronic, and that its sensitive to too much loop current -- and
the DSL filter drops the current far enough for that 'relay' not to
pull in spuriously.
|
Yes, I was suspecting it was something like that. I bought a 33-ohm
resistor (1/2 watt) and it fixed the problem. Both modules are working
properly now.
According to the Ohm's law, the loop's overall resistence was 188.46
ohms, once I was measuring 4.9V and 26mA in the circuit. By adding 33
ohms, it went to 221.46 ohms, bringing the current down to 22 mA.
| Quote: | Telecom guy Mike Sandman has a paper on loop current on his website:
|
Excellent article and telephony stuff. Bookmarked!
Thanks for the reply. Have a nice day.
--
MARLON DUTRA
Propus
GnuPG ID: 0x3E2060AC pgp.mit.edu
http://www.propus.com.br/
http://hackers.propus.com.br/~marlon/ |
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