Brainteaser of the month

[tiggerpaws]

With digital lines, sometimes SIT tones
are not always effective, I wonder, is it
possible to cause asterisk to generate such
a message on a digital line to telemarketers
whose number that you route to a particular
destination to do such a thing?

Right now, I have one analogue line and
two digital lines coming
in (the digital lines come in over a DSL line
and I make the short-short-long SIT
play on the analogue line if telemarketers call in
on it, sends to destination 999 for example.

But, on my digital IPKALL line, I wonder if it
is possible to send a robot caller to
such a destination that instead of the
SIT, it sends a signal through the
digital channel that does this, a messsage
that would tell the robo dialler that the
number is not in service, the digital
equivalent of the old SIT tones?

Fellow Nerds, let us discuss at will.

 

[billsimon]

Ipkall is not digital. It's IP (SIP/RTP).

Analog = copper pair = POTS. FXO/FXS port on a device interacts with the provider (telco) using analog signaling (inband audio signals, voltage levels).

Digital = T1 PRI, for example. Interface card interacts with the provider using ISDN protocol in this case.

IP = SIP, IAX2, SCCP, MGCP...

So send the appropriate SIP signals back to Ipkall when you get a telespammer. The SIT is basically a way of saying "wrong number" or "not found" in analog parlance, so use SIP code 404 ("not found") to signal back to Ipkall a 404, which should pass the signal along to the caller (using whatever protocol is appropriate!) that they have dialed the wrong number.

The way to send a "not found" signal over SIP using Asterisk is the dialplan application Hangup(1). (A normal hangup is Hangup(16)). See http://www.voip-info.org/wiki/view/Asterisk+cmd+Hangup Asterisk is taking ISDN User Part codes as arguments to the Hangup command and if the channel is SIP, converting to SIP codes. (http://www.ietf.org/rfc/rfc3398.txt)

So you can set up a custom context in extensions_custom.conf that pretty much just runs Hangup(1) and then direct your telemarketers there via inbound route. But be sure not to Answer() the call first!

The reason Zapateller isn't successful with some telemarketers is that it actually sends an Answer (SIP 200) and then sends the inband audio indicating an error. It's a mixed message that says I'm here but wait there's no one here. It might fool some equipment that is just listening for tones.

 

[tiggerpaws]

I could type something like this
in the extensions_custom.conf file?

[998]
exten => 998,n,hangup(1)

then direct said calls to this
misc destination?

 

[billsimon]

That's the right idea but you've got some errors.

Try something more like...

[custom-hangup-notfound]
exten => s,1,Hangup(1)

and then setup custom-hangup-notfound,s,1 as your custom destination in FreePBX, and direct your callers to that.

(You can't use 'n' as the first step in a context.)

 

[tiggerpaws]

Ok I typed that in the
extensions.custom conf file
and I cant find it, it does
not show up in freepbx interface,
where did it go?

I can't find a custom-hangup-notfound
in the misc apps or dests.

 

[billsimon]

It won't appear automatically. You have to type it in yourself to Custom Destinations then it will be available in the rest of FreePBX.

For example if you do exactly as we have discussed you'd enter "custom-hangup-notfound,s,1" (without quotes) as the custom destination and then save it. Then elsewhere in FreePBX you can choose that.

 

[tiggerpaws]

Found it. WORKS.

Wow, it even works some what on
the analogue line, the system plays
the regular SIT and then drops
the call on a blocked number.

(I tested with a cel phone hehe)

So far it seems to work, the recording
one hears in the audio channel is
the phone co's own error message,
this really cuts down on system resources
as well, as it does not have to play
any recordings, just sends a digital
message and hangs up.

I think I like this method much better
for all lines, now I can just plop those
telepests in that destination and
PUFF! No more pest calls, well, much
less anyway.

Many thanks for all the info,
will also let all know how it works
out down the road.

 

[tiggerpaws]

Update:

I had a duh moment, it was not
"automatically" working with the
analogue line, I was half alseep.

I had the system on "lockdown"
so of course it appeared to
work this way, what actually
happened was it tried to send
the 404 down the analogue
line and of course that does not
work so it just disconnects,
ie, the "hang up" command.

But, calling the local digital
line with the local analogue
line proved to be very cool,
I heard (over the analoge line)
the local phone co's own
disconnected message, not
the one generated by the pbx.

Very Cool.

Thank you all again very
much for this info.