How would I make this landline system?

Edit: no idea if this is the right forum, please lead me to the correct place if this isn't.

I have some experience in Java and want to learn as much as I can of the language.

Basically, what I want to do is to use something like this and make my application in Java that will handle calls between, let's say 4 phones.
I expect as little traffic as 1 active call at once.

Anyways, what the system should be capable of: have a list of numbers. Every number has a dedicated USB port. That USB port has the dongle previously mentioned. The phone connects to the dongle.

Now, what I am struggling on finding information about: I need to know how to understand when a phone is dialling, and how to transmit the voice signal. I need to know how to ring the phone at the other end. I can figure mapping phones to numbers easily, I just need to know how to convert the electrical signal (that I get from the USB) to a phone number. Are they sent in ANSI? Are they sent in some other protocol? Please help.

Post was last edited on July 18, 2019 4:10 PM PDT

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Not to discourage you.

But if these are programmable then the maker supplies the usual API and documentation. If not, the hardware is not something you can use and you begin your search again.

I've had folk ask me similar questions and they don't know what an API is. Please take time to research that plus ask the hardware maker if they have such available.

Finally, only your newest developer would restrict the coding language. If the API is for C++, then you code in C++.

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I am a bit unsure as to what you are refering to.

What are you referring to? I was thinking of just getting the signal via a USB library and transmitting it to the recipient somehow, but I need to know who the recipient is, and to do that I suppose I should detect for some electrical signal? Or something? Really, all I need is to understand how landlines send the number they want to access, and how to ring them (and of course how to transmit the voices).

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If you meant the phone itself, I'll look it up but I am pretty much sure they should use one standard for all phones using RJ11 for example.

Post was last edited on July 19, 2019 1:43 AM PDT

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Re: RJ45

RJ45 is for Ethernet. Phones use a smaller plug called RJ11 (see ).

Moreover, it's analog, while USB is digital. So you would have to use some A/D-converter to connect. tells more about the usual hardware. Be sure it comes with enough documentation to enable you to make your digital exchange.

To learn programming, I'd start with a simulation in stead of the real thing. One of my first assignments in OO programming with Java was to simulate a crossing with traffic lights that should react on incoming cars. No real lights and real sensors were involved.

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Re: Re: RJ45

I corrected myself about RJ45, to RJ11. Also, I never said I want to learn programming. I want to know how to ring the phones and understand when a phone is dialling.

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Re: phones

In your thread starter you said "I have some experience in Java and want to learn as much as I can of the language." Sorry if I summarized that incorrectly as wanting to learn programming.

Analog phone lines transmit sound, as told in .
Most sounds are your voice (with a limited frequency range); certain frequencies are signals, as told in .

But if you use an analog telephone adapter as in my post above, you don't need to know anything about it. It's all translated into nice digital signals if you get it into your computer.

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get a PBX system?
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Pbx system

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