Subject: RE: [Megaco] ON-OFF signals in signal list

From: "Kevin Boyle" <[email-masked]>
Date: Mon, 7 Nov 2005 14:56:59 -0500

To confirm Jon's statement:

Any polarity reversal or other signalling that is an inherent part of
the CallerID function is implied in the andisp/dwa signal.  This is
explicitly stated in H.248.23.  The intent is to avoid this kind of
signalling snafu, especially since the line reversal is not related to
the ringing portion of the signal (well, other than the fact that
callerID and alerting are always done in conjunction with each other).

Take the following example of why this is an important distinction:
When data transfer fails, the CPE is still supposed to provide the
alerting (ringing in this case).  What if the MG has had a failure in
its CLASS modem function?  It may choose not to bother with the line
reversal, because the CID function is doomed to failure anyway.  But it
STILL must provide ringing.  By using signal list, the MG would report
back an error to the MGC, which may result in the call failing!

Kevin 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Richard Sun
Sent: Monday, October 17, 2005 2:24 PM
To: Jon Rowland
Cc: [email-masked]
Subject: Re: [Megaco] ON-OFF signals in signal list

Jon,
Your example is great to understand how the protocol works.
Thanks a lot.
-Richard

Jon Rowland wrote:
> Richard,
> 
> If this is a regional requirement whereby ringing and callerID require

> the line to be set to reverse polarity, then I'd say the best solution

> is for the MG to be aware of its local requirements and implement 
> alert/ri and andisp/dwa in such a way that it reverses the polarity 
> with the right timings as part of playing the base signal. You could 
> even get rid of specifying xal/las entirely (as it's intended for 
> Line-side Answer Supervision, as the name suggests). MGs already need 
> to know how to implement andisp/dwa differently as the caller ID 
> format, and timings are different in different regions, this just 
> feels like another variant, if I'm understanding it correctly.
> 
> That said, as a pure thought exercise, how about the following nasty 
> solution? :-)
> 
> You need to be able to play a 'do nothing' signal on the termination.
> Something like qtlt/quietterm would be the right sort of idea, 
> although it's obviously a nasty hack. Then override the signal type to

> timeout and give it the duration of your intersignal delay (X), and 
> use an embedded signals descriptor to play the caller ID at the right 
> point based on the completion of the QT signal. You get something like
this:
> 
> Modify:
> Signals{xal/las, qtlt/quietterm{NC={TO}, DR=X}} Events=1{g/sc, 
> EM{Signals{xal/las{KA}, andisp/dwa{ddb=etc...}}}
> 
> I think this does the trick logically, although MGs may not support 
> it, and I certainly don't recommend it as a real-world solution - just

> something to entertain me on a Monday afternoon! :-).
> 
> Cheers,
> Jon.

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