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To create a little VoIP system you need the following hardware:
All that has to be present twice to simulate a standard communication.
The tool above are the minimal requirement for a VoIP connection: next we'll see that we should (and in Internet we must) use more hardware to do the same in a real situation.
Sound card has be full duplex unless we couldn't hear anything while speaking!
As additional you can use hardware cards (see next) able to manage data stream in a compressed format (see Par 4.3).
We can use special cards with hardware accelerating capability. Two of them (and also the only ones directly managed by the Linux kernel at this moment) are the
Quicknet PhoneJack is a sound card that can use standard algorithms to compress audio stream like G723.1 (section 4.3) down to 4.1 Kbps rate.
It can be connected directly to a phone (POTS port) or a couple mic-speaker.
It has a ISA or PCI connector bus.
Quicknet LineJack works like PhoneJack with some addition features (see next).
For more info see Quicknet web site .
Quicknet LineJack can be connected to a PSTN line allowing VoIP gateway feature.
Then you'll need a software to manage it (see after).
We can choose what O.S. to use:
Under Win9x we have Microsoft Netmeeting, Internet Phone, DialPad or others or Internet Switchboard (from Quicknet web site ) for Quicknet cards.
Also you can use free software you download from OpenH323 .
Under Linux we only have free software from OpenH323 web site: simph323 or ohphone that can also work with Quicknet accelerating hardware.
Attention: all Openh323 source code has to be compiled in a user directory (if not it is necessary to change some environment variable). You are warned that compiling time could be very high and you could need a lot of RAM to make it in a decent time.
To manage gateway feature (join TCP/IP VoIP to PSTN lines) you need some kind of software like this:
You can choose as gatekeeper:
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