[asterisk-users] Linking Asterisk with PBX through E1

Marlon Dutra mfdutra at gmail.com
Tue Sep 5 13:40:28 MST 2006


I linked an Asterisk server to a Brazilian PBX (Leucotron) through an E1
connection, using MFC/R2, that's common down here. The connection works
properly. I'm able both to dial and receive calls through that link,
among their extensions.

The problem is that the PBX configuration is very tough. Just a few
options in the GUI software and I cannot play with it in lower level.

That PBX has two E1 interfaces. One of them is connected to the PSTN and
the other to the Asterisk server. Both connections are working ok.

I need to make calls from the Asterisk server to the PSTN, i.e., coming
from an E1 and going through the other one. Here is my pain. That PBX
assumes that an E1 connection is "always" PSTN, so an E1 link doesn't
need to talk to each other. Zero flexibility.

The manufacturer support gave me a "solution". Coming from Asterisk, I
can dial a special code, then I get a simulated dial tone, and then I
dial (through DTMF) the number I want. That's odd, but it works.

In my case, that code is 6666. Since E1 is digital-signaled, the best to
do would be dialing just like I do between two Asterisks:

exten => _XXXXXXXX,1,Dial(Unicall/g1/6666${EXTEN})

But it doesn't work. The PBX just ignores the numbers after 6666 and
gives me a dial tone.

Another way would be dialing 6666 and then sending the "number to dial"
through DTMF tones, with something like this:

exten => _XXXXXXXX,1,Dial(Unicall/g1/6666|20|D(w${EXTEN}))

That would work, BUT a little detail broke my legs. The "Dial"
application only sends the DTMF tones after receiving the "channel
answered" signal from the E1 channel, and that PBX only sends that
signal when the remote party has answered the call, what's useful for
accounting purposes. So, when I dial something using the above dial
plan, Asterisk dials 6666 and I hear the dial tone. If I dial something
in my phone (DTMF), the PBX hears that and makes the call. When the
remote party answers the call, the Dial application releases the DTMF

Possible solutions:

1) Finding a way that Asterisk sends the DTMF tones immediately after
opening the channel, without waiting the answer signal.

2) Making the PBX works the way it should do, receiving all the numbers
in the digital channel and making the call without simulating any dial

I'm not hopeful that the manufacturer will be able to change the way the
PBX works, so I better keep looking for the first solution.

Any help is pretty welcome.


Marlon Dutra

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