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

[Peter Svensson]

On Thu, 18 Nov 2004, Rich Adamson wrote:

> Examples:
> 1. two-wire analog pstn lines: as soon as current draw is sensed by
> the central office, answer supervision is generated by that "central
> office", period. It has nothing to do with whether * handled it or
> whether an analog phone is hanging on the end at the customer's
> location. There is no such thing as one-way audio or grace periods.
> 2. Trunk lines from the Central Office to a customers site: can be
> configured at the central office in many different ways and is
> dependent on the "service" requested/provided. One-way audio, grace
> periods, etc, are oftentimes dependent upon exactly which Central
> Office switch the telco is using (eg, Nortel, Siemens), and whether
> the telco "chooses" to support those options.
> 
> A PRI is considered a trunk line; a BRI is not. An ordinary analog
> pstn fxo interface is not a trunk.

Early audio b->a is an option in isdn. It is quite common in 
EuroIsdn-land. Even on a bri. There seems to be a large difference in 
mindset between US and European countries. In the US isdn is just a fancy 
form of the old trunk lines. You pay for everything you want enabled. In 
some (most?) EuroISDN-countries a lot if stuff is considered basic isdn 
setup and has no extra cost associated with them. Reverse audio, caller 
id, etc.

Isdn can certainly emulate old copper wires with their limitations. I 
guess it is up to how greedy the pstn provider is, or what they can get 
away with.

Peter