[asterisk-users] T1 Wire Level Tapping

[Shane Spencer]

I am very interested in the DACs capabilities of Digium cards, there
is no information anywhere on this.  I could always do pri bridging
via libpri like you suggest however.  But having hardware handle the
bridging onboard a single PCI card would help reduce my server
requirements for a final product, as long as I can spy on active
channels somehow.  I don't think its going to work that way, I wil
test out libpri for a bit.

Shane+

On 1/28/07, Leo Ann Boon <leo at datvoiz.com> wrote:
> Shane Spencer wrote:
> > I am trying to do a wire level tap on T1 equipment using digum
> > equipment.  So far most call monitoring hardware for call centers try
> > to stay on the analog side requiring a lot of rewiring.  I have
> > already posted to the list about T1 "bridging" using DAC's support in
> > the zaptel drivers.  I still don't know if I can spy on channel
> > information since I don't have any digium hardware on me until the
> > project begins.
> >
> There are a number of systems using ISDN digital taps. The proper way
> requires a high impedance bridge - you don't want to load the line that
> you're tapping.
>
> > Anybody found a method of spying on a D-Channel and all voice channels
> > using standard T1 equipment?  I am making a rough assumption that if I
> > can trick the zaptel drivers into operating without anything
> > responding to a TX signal then I can do the following:
> You can directly bridge the 2 ports and extract what you need as you
> bridge - see pridump.c in libpri. You don't even need asterisk, just the
> zaptel and libpri. The only problem with this approach, is that the
> bridge becomes a point of failure. Your box down, your PRI goes down as
> well.
> >
> > S-T1 = T1 to Spy On
> > T1-1 = Digium T1 card #1
> > T1-2 = Digium T1 card #2
> >
> > Map S-T1(RX) to T1-1(RX) and S-T1(TX) to T1-2(RX) and decode the
> > D-Channel where appropriate, should I be able to spy on the RX/TX
> > channels enough to make a recording including CID information?  This
> > would help in situations where the monitoring system needs to be
> > replaced or taken down without bothering in-progress calls.
> This is technically correct, but I don't know how well it works. Eicon
> recommends a similar technique to do monitoring with their Eicon Server
> cards. For the BRI, it's done this way. But for the PRI card, they
> actually suggest using a custom cable. Eicon cards have a special Hi-Z
> monitoring mode to support this application.
> http://www.eicon.com/worldwide/solutions/How_To_Call_Tapping_and_Monitoring_with_Diva_Server
>
> FYI, Voicetronix has a Hi-Z version of their OpenPRI card that work with
> an open-sourced voice logging application available from their site.
>
> Leo
>
>
>
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