help on design

[cisbob]

I have some ideas for the use of ISDN in none-telephone applications (but similar). I need some help from someone who understands how to put ISDN together, including coding at the exchange equivalent to see if the idea I have is viable.

I am not a company and this is not a job offer.

 

[ISDNman]

Not sure what you mean by "coding at the exchange". If you mean writing an ISDN protocol stack that would emulate an ISDN LT (line termination) that is extremely complex. The vast majority of vendors buy their protocol from a few highly specialized companies that specialize in this stuff. For example Telsoft.

Some, but not all, ISDN stacks support both NT (Network temrination, for use in CPE) as well as LT. Many offer NT only however.

If you can ask more specific questions I'll try to answer them.

 

[cisbob]

It might be best to explain what I want to do. I wish to make an intercom system based on ISDN (or even DSL). All users will talk to each other with full voice conferencing. In addition to this users will require data access to the system.

The system will allow users to sect a particular external device to speak over (susch as a simplex radio) and/or send data over via RS232.

My view was it is not too disimlar to a telephone exchange and the ISDN would give it its data capability.

Any views?

 

[chris13]

It is possible use ISDN for such an application.
Sounds like building an ISDN multimedia switch...
You can choose a service-indicator (voice, data, video etc...) per call (channel).
If you want to integrate IP-networks for data and VoIP you'll have your app to control connections and voice-/data-switching on a higher level. Then translate to the protocols used by different media (CAPI, SIP, H323 etc).

How about using existing platforms like asterisk?

See

http://www.linuxlinks.com/Software/Internet/Communications/Telephony/

 

[ISDNman]

Will the public Telephone network be involved at all?

In order to conference all these parties together you need a digital switch. Ingress and egress from the could be via ISDN, or any other way.

A lot of this depends on weather some of these intercom stations will be off-premises. In this case you may want to use circuit switched telephony for access and in that case ISDN would be a good choice.

The biggest advantage to ISDN is that it is 4 wire (eg separate send and recieve paths) all the way through so the conferencing can be done in native 4-wire mode rather than having to use hybrids to cancel out leakage. Of course if it won't be ISDN (or other 4-wire digital) end to end then a hybird would still be needed for optimal performance.

You may want to look at existing Intercm systems versus reinventing the wheel. Google some of the following to see what is out there:

Clear Com

Telex

Reidel

Trilogy

Good luck