[Asterisk-Users] Re: How to generate "ringing tone" to a calling party.

[Jay Hennigan]

> Actually, this is required to work for telco's (I would think this is
> the same in most countries). Consider premium rate phone services (in
> Australia, 1-900 xxx xxx) where you are charged $x per 'time unit'. eg,
> $5/minute etc... The service operator is required to tell you how much
> the call will cost, and allow you to dis-connect and avoid all charges.
> Of course, the way this is done is to play the message before answering
> the call. Once you answer the call, the telco begins charging, and you
> begin providing the 'service'.
>
> As I said, I would be interested in being able to deploy this properly,
> as it means that people calling from long distance/mobiles don't have to
> pay while they are waiting for a real person to answer. I imagine this
> would also have a rather positive effect for people who have inbound
> 1300/1800 numbers (where you are charged for the incoming call, I assume
> from the time you answer the call).
>
> PS, also, premium rate numbers (1900) you are not permitted to have the
> caller on hold while you are charging them etc, so again, I assume you
> would need to not answer the call until they are actually connected to
> the operator...
>
> This may work differently in other countries, I may be totally wrong,
> etc...

Speaking for the US, and conventional telephone systems, audio from the
called end to the calling end is cut through before answer supervision
is returned.  This means that the called switch generates the audible
ringback which is carried through to the caller.  Audio from the caller
toward the called party is muted, and there is typically a timeout of
two minutes or so on ringing.  (We just tested this today as part of a
battery of acceptance tests on some gear.)

This allows the called switch to not only generate audible ringing but
also an intercept recording, "The number you are calling has been changed,
the new number is...", "All circuits are busy now...", etc.

I don't think the 900 pay-per-call services use this model, but instead
have a built-in "grace period" in the billing mechanism after answer.

--
Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net
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