[VoIP] Tandem Stacking over Asterisk

[Donald Froula]

There is a recording of the new timing parameters
applied to a 24 SF trunk stack at the end of the
recording at 1-762-0171. Use # to fast forward, * to
rewind.

Don

--- Donald Froula <dfroula at sbcglobal.net> wrote:

> I also changed rxwink=150. It now takes 150 ms. of
> 2600 to seize the trunk. This also lengthens the
> forward disconnect time on each link in the forward
> stack, so you can hear the individual cheeps of 2600
> as the stack is torn down. It's slow enough you can
> count the links.
> 
> Don
> 
> --- Donald Froula <dfroula at sbcglobal.net> wrote:
> 
> > I changed the setting of "toneduration" in
> > /etc/zapata.conf from 68 ms. to 100ms. This
> > increases
> > the duration of the MF tones on the SF trunk group
> > during call setup, but also increases the length
> of
> > regenerated DTMF tones sent down the line. This
> > enhances the "flash forward" effect on a tandem
> > stack
> > by extending the propagation time through each
> link.
> > 
> > The reason one gets a hook-flash effect when
> dialing
> > DTMF through the stack is that The ATA receives
> the
> > DTMF digit, converts it to a SIP message, Zaptel
> > converts back to audio on the first SF trunk link,
> > Zaptel converts back to an internal message on the
> > receiving end, then back to analog DTMF on the
> next
> > link and so on. This adds a 100 ms. delay for each
> > link on each flash of a DTMF digit down the stack.
> > 
> > Don
> > 
> > --- Donald Froula <dfroula at sbcglobal.net> wrote:
> > 
> > > This actually sound pretty amazing while
> listening
> > > on
> > > the far end, if one dial an extension on the
> last
> > > loop. When the originating end goes on-hook, you
> > can
> > > hear the string of kercheeps as the call
> > > disconnects,
> > > one for each link. If the originating end taps a
> > > touch
> > > tone digit, you can hear a series of clicks as
> the
> > > tone propagates down the stack. Sounds pretty
> much
> > > like the Classic Stacking recording!
> > > 
> > > If you want to try, here's how:
> > > 
> > > - Dial my ProjectMF trunk on 1-762-2601 (or
> > > 1-762-2602, skipping the net two steps, for
> those
> > > without a blue box)
> > > - Blow off the ringing with 2600
> > > - After the wink, dial KP-2602-ST
> > > - Wait for the dial tone
> > > - Dial 2602 with the DTMF pad of the phone
> > > - Wait for another dial tone
> > > - Dial 2602 with the DTMF pad
> > > - (Repeat X times, up to 23 times, as desired)
> > > - On the last dial tone, dial a number on CNET
> > with
> > > 011+CC_Number, again with the DTMF pad
> > > - Answer the ringing phone. You are now talking
> to
> > > yourself over X number of SF trunk links
> > > - Hit a touch tone digit onthe originating
> phone.
> > > Listen to it flash down the stack.
> > > - Hang up. Hear the stack disconnect with a
> cheep
> > of
> > > 2600 for each link
> > > 
> > > Notice how the connection takes longer to return
> > the
> > > dial tone on each loop through the stack, as the
> > > audio
> > > delay on the forward MF (which you can't hear)
> > gets
> > > longer and longer.
> > > 
> > > Regardless of how you come in. you can blow the
> > call
> > > off in the forward direction with 2600 and hear
> > the
> > > stack disconnect on the far side.
> > > 
> > > Much fun!
> > > 
> > > Don
> > > 
> > > PS - For those without MF and 2600, I set up
> > direct
> > > access to the SF/DISA arrangement on 1-762-2602
> > > 
> > > Note, if others are trying this, your available
> > > trunk
> > > pool may be less than 24.
> > > 
> > > --- Donald Froula <dfroula at sbcglobal.net> wrote:
> > > 
> > > > I hit upon an approach to try this trunk
> > stacking
> > > > thing through my TDM-Over-Ethernet SF/MF
> trunks.
> > I
> > > > set
> > > > up two extensions to go to DISA over the
> trunks.
> > > > What
> > > > I do is dial the extension that goes over the
> > > trunks
> > > > (similar to my 1-762-2601 number), but instead
> > of
> > > > programming the number that gives ringback in
> > the
> > > > Dial
> > > > command, I call another extension with the
> DISA
> > > > application that returns a dial tone.
> > > > 
> > > > 2602 => 1,Dial(ZAP/g1/9999)
> > > > 
> > > > 9999 => 1,DISA(password|from-internal)
> > > > 
> > > > I then dial the same number again (2602),
> which
> > > > seizes
> > > > the next line and gives a DISA dial tone
> again.
> > > This
> > > > is all via DTMF, so, yes, I am cheating.
> > However,
> > > > the
> > > > call setup on each loop through the trunk
> group
> > is
> > > > via
> > > > 2600 and MF.
> > > > 
> > > > I saturated all 24 lines of the trunk group
> this
> > > > way,
> > > > dialing one of my Evan Doorbell recordings on
> > the
> > > > last
> > > > trunk. The audio was looping through all 24
> > > > SF-controlled trunks. Both sides of the
> > connection
> > > > being on the same switch, I only noticed
> slight
> > > > degradation in the audio. I blew off the call
> > with
> > > a
> > > > chirp of 2600. This sounded exactly like
> blowing
> > > off
> > > > a
> > > > call on a single trunk, except for the 24
> > > disconnect
> > > > mrssages that flew by on the Asterisk console.
> > > > 
> > > > Now, if the looping could be done through
> > another
> > > > ProjectMF switch, it might sound interesting.
> > > > 
> > > > Don
> > > > 
> > > > --- Donald Froula <dfroula at sbcglobal.net>
> wrote:
> > > > 
> > > > > Mark, you asked about whether or not a 2600
> > > audio
> > > > > blip
> > > > > might get propagated through the system for
> > 2600
> > > > > flashes less than rxwink in length.
> Actually,
> > > they
> > > > > would. The 2600 notch filter DSP code takes
> a
> > > > > millisecond or so to kick in and out,
> creating
> > > an
> > > > > audible "blip" both on 2600 application and
> > > > removal.
> > > > > Although this has no effect on supervision,
> > > being
> > > > > purely an audio effect, it might provided
> > > > something
> > > > > like the old sound with the latency delay
> 
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