[VoIP] Seize zap channel without dialing

Fri Sep 28 07:51:25 CDT 2007

Hi, Mark. Good to hear from you "down under",

I corrected the trunk-hang problem by a patch I added
to Asterisk that restored 2600 supervision based upon
steady-state 2600. It sounds odd, but seizure of the
trunk with the original set of patches was based on
REMOVAL of steady 2600. Applying steady 2600 after
seizure did not disconnect the call. This was to allow
the user to 'box another call after the previous far
end call disconnected. Evan Doorbell calls this a
"goody" trunk in his recordings. I accomplished the
"goody" arrangement after my patch by changing some
settings in /etc/zaptel.conf. Short answer: The trunks
now disconnect correctly from stacking attempts.

It is true that the timing of the minimum 2600 tone
duration to seize and also the length of the reverse
wink can both be set by configuration settings in
/etc/asterisk/zapata.conf. I have mine set to
rxwink=50 (requires a minumum 50 ms. of 2600 to seize,
for talkoff protection) and wink=250 (sets
acknowledgement wink to 250 ms.). The "wink=250"
setting is purely cosmetic, as the near-end trunks are
using immediate dialing, and is just for realism and
an indication to the 'box user that the MF receiver
has been successfully attached to the far end.

What you are asking is whether or not 2600 bursts
shorter than the setting of rxwink will cause a
momentary application of supervision that will not
disconnect the call. This was called "ring forward" or
"operator flash" in the old days. Unfortunately,
ProjectMF completely ignores any forward application
of 2600 that is less than rxwink in duration. Reverse
2600 is completely ignored. In the forward direction,
anything greater than 50 ms. simply hangs up the call.
There is no intermediate state to allow the wonderful
sound of all those relays clattering you can hear in
the "classic tandem stacking" recording on Phonetrips.
In the reverse direction, the notch filters are still
operative, but I have 2600 supervision disabled by the
settings in /etc/zaptel.conf to "goody" the call.

If I can figure out how to dump into a seized trunk
without dialing anything, allowing the 'boxer to MF
without the 2600, stacking should be possible. The
accumulated echo might be interesting. It would
probably drive the Zaptel echo cancellers nuts! Right
now, the 'boxer needs to blow 2600 on each successive
link to restart the MF receiver, but this disconnects
back to the first link. Maybe some kind of "guard
banding" would work to blow off the last link while
leaving the rest of the stack untouched, but I doubt
it.

Your trunk simulator sounds very interesting. I wonder
if it can be integrated with ProjectMF very easily. I
received a very nice note from Evan Doorbell regarding
my system. He found it interesting, but, without the
complexity of the old system, of limited interest.
Still, I think it's pretty cool to be able to blue box
at all. I guess that thrill has gotten hard-wired into
my brain somehow! I've borrowed lots of ringback
sounds from Evan's "long distance ambrosia" tape of
high-quality long distance call completion sounds.

Try the system, if you haven't recently. It's working
very well, now on a new dedicated server with proper
power backups and auto-boot recovery capability.

Best,

Don

--- Mad Mark <madmanmarkau at hotmail.com> wrote:

> 
> Hey Don. I've been lurking for a while but had to
> post when I saw this.
> 
> I remember we discussed this a while back over
> E-Mail. You had tried stacking by dialing out of
> your system and dialing back in, trying to stack the
> call. You said it caused the system not release the
> trunks further down the line when the call hung up,
> and the system needed restarting to rectify the
> problem. Are you still having this problem, or was
> it sorted?
> 
> Now, if you're able to stack on a ProjectMF system,
> from what I've been able to discern flashing the
> hook-switch won't work, correct? I've been wrong on
> many an occasion before, and am just starting to
> learn the quirks of ProjectMF.
> 
> I think I've got this right. Tell me if I'm wrong.
> As long as the 2600 supervision "flash" you send is
> not longer than x milliseconds set in the config
> files, ProjectMF shouldn't disconnect the call.
> HOWEVER, even on short flashes, will you still get
> the "bip-bip-bip-BIP-BIP-BIP-BIP" effect (the 2600
> flash traveling from exchange to exchange) on a
> ProjectMF system? I'm thinking you won't without
> more "cosmetic" coding.
> 
> Work on the exchange emulator is progressing much
> slower than I anticipated, mainly due to lack of
> time (and motivation) to work on it. I have,
> however, almost completed a wire-carrier trunk DSP.
> 
> For those that don't know, I'm slowly writing an
> actual phone network emulator to run on your local
> machine, able to simulate many different exchange
> types/configurations and trunk types, all with the
> old sounds (panel-pulses, SxS noise, XBT sounds,
> carrier noise...).
> 
> The only part I have completed so far is audio I/O
> and one trunk type, as well as miscellaneous other
> items. The trunk has programmable dynamics, having
> adjustable frequency response, looping wave file for
> carrier noise, and new as of last night, the
> "singing wires" effect (which I'll complete and test
> tonight.)
> 
> Sorry about the long message, but I tend to rant...
> 
> 
> >From: dfroula at sbcglobal.net
> >To: voip at ckts.info
> >Date: Thu, 27 Sep 2007 08:25:56 -0700
> >Subject: [VoIP] Seize zap channel without dialing
> >I wonder if anyone knows how to do accomplish the
> >following.
> > 
> >I want to be able to seize one of my SF/MF Zaptel
> >trunks without dialing any digits.
> > 
> >I normally route a call through my T1-Over-Ethernet
> >trunks with a simple dial command like:
> > 
> >exten => 2600,1,Dial(ZAP/g1/999)
> >exten => 2600,2,HangUp
> > 
> >This dials extensions "999" through the SF/MF
> trunks,
> >and allows the blue box user to seize the ringing
> 999
> >extension with 2600.
> > 
> >I want to be able to simply seize the line without
> >dialing anything, allowing the user to "stack"
> calls
> >without having to blow 2600 and release the entire
> >stack. Just seizing the trunk on connecting would
> >allow the blue box user to simply outpulse the MF
> >digits within the trunk timeout window (5 seconds
> or
> >so), similar to the Phonetrips "classic tandem
> >stacking" recording.
> > 
> >I tried omitting the extension:
> > 
> >exten => 2600,1,Dial(ZAP/g1/)
> >exten => 2600,2,HangUp
> > 
> >This doesn't work, since KP-ST with no digits still
> >gets sent, routing the call do the default
> extension
> >in my incoming trunk context.
> > 
> >I hope this all makes sense.
> > 
> >Any ideas?
> > 
> >Don
>  
>
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