[VoIP] Real-time dialling and tandem stacking

[ikjtel]

In brief, here's what might be required to move
forward on this...

1.  Establishment of direct interoffice trunk groups
between offices.  From the perspective of the SxS
office, this should be largely identical to how things
would have been done in real offices in the old
days...

2. For the outgoing leg of the trunk, the outgoing SxS
selector levels would terminate on some sort of zaptel
"FXS-like" instance within asterisk.  Asterisk would
be set up to send SF signalling outward on these ports
(essentially DC-to-SF conversion).  It's been a long
time since I looked at this, but if I recall
correctly, this is a standard Zaptel feature and would
require no extra patching.  It's not immediately clear
how the "S" lead signal would be generated back to the
selector, but I'm sure someone has already solved that
problem...

3. The asterisk routing would presumably be set up
such that these calls would be specially tagged
somehow to identify them as direct interoffice trunk
calls rather than ordinary CNET user calls.  When
siezed in the outgoing office, asterisk would
automatically initiate a VOIP connection to the proper
destination in the called office, based on the
selector level that was selected.

4. Incoming from the VOIP world, the direct
interoffice trunks would be mapped to zaptel FXO ports
that would then terminate on incoming selector levels
on the EM machine.  Presumably the EM office might be
arranged not to return dial tone on these trunks.  The
zaptel driver on this leg of the call would require my
"2600/SF" patch in order to reconvert the pulses from
SF to DC for application to the incoming selectors in
the called office.  Multi-hop operation should not be
a problem, since the SF patch is configured to notch
the 2600 and not pass it forward to succeeding legs of
the call...

5. When the caller initially connects to the first SxS
office in the connection, it might be set up to simply
give them access to a first selector which returns
dial tone without any initially-dialled digits (i.e.,
unlike in CNET today).  The caller would connect, hear
the dial tone, and begin dialling using SF
outpulsing...

6. Channel-bank FXO should be used throughout instead
of X100P in order to provide a realistic listening
experience...

Max


 
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