C# – create a dialtone from 56k modem

cmodemmscomct2.ocxserial-portvb6

Ok, everybody get in your wayback machine. I need to have a phone dial into my computer's 56k modem. I need my computer to have the modem "on" and have an active dialtone.
Here is why:
I have a sump pump alarm that will call me on a pump failure. It only works with a landline. I want to stop paying for my landline to save money and just have my cell. My idea is to intercept the outbound caLL from my sump alarm on my pc's 56k v90 modem. Then I can text message, email,etc… for free.

Does anybody know how to get started? I have found plenty of stuff on how to make outbound calls from my pc, but I want a phone (device) to dial my pc. I think the sump alarm will not dial unless it hears a dialtone.

I prefer a C# or vb6 program, but willing to go with anything. I have some experience working with serial comm devices so I just need to be pointed in the right direction.

Thanks!!!

Best Answer

You're going to need more than a modem in your PC to accomplish what you've described. Both the sump pump and your PC have modems, which are the subscriber end of a telephone "loop". The CO end (Central office in telephony terms) provides functions that you're telephone and both the modems mentioned above.

A big one is the generation of a ring ... this is a relatively high voltage AC signal that actually rang the bell in the old style telephones, but is simply detected in newer phones and your modems. In order for your sump pump's call to be recognized, this ring voltage has to be received at your PC's modem, but the sump pump won't actually generate this tone.

The other ideas presented here (the use of a PABX SOHO switch or connecting the detected signal from the sump pump directly to a I/O port on your PC), I can think of one other option. Somewhere inside the sump pump is a UART chip that does the serial communications to the included modem. If you disconnect the modem from the UART, you have the basics of a serial port, which can be connected to the serial port on a PC (though you may need an interface chip to get the levels right ... see the ICs provided by Maxim).

Good luck!

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