OK as to the software. Here is what I did. I wrote a very simple program in old ancient VB 6 (Visual Basic 6.0). Originally this little program was used to monitor the digital I/O lines (Not the data lines) of the RS 232 port. WE will get into the code later but for now the form looks like this:
**broken link removed**
On the bottom of the form you see a button labeled Disabled. If we click that button the form sprouts more features and will look like the below:
**broken link removed**
A few things to note. The RS 232 port will have a COM Port Number. On the top of the form you must select the port FIRST before clicking Open The Port! Once the port is selected then click open the port. The program will show the status of the three DI (Digital In) lines of the RS 232 port. I have actually used this with a Dongle connected to the USB port (USB to RS232 Dongle Adapter) and it works fine.
The program can be downloaded here.
The program is in a Zip folder for download. Download the folder to the location of your choice and right click it and extract the files to a new folder. You should see a Setup.EXE and if you double click it the program will install. Just follow the prompts and the program can also easily be uninstalled using a normal uninstall procedure. It is only a few MB and will run on just about any OS.
Now without clicking the Phone Home button and leaving it disabled just run the program. Try jumping Ground (pin 5) on the RS 232 port to pins CTS, DSR and DCD pins 8, 6, and 1 respectively. You should see things happen. Let's make sure that much works.
The pins are Digital In, the must be a 1 or 0 with 0 being a grounded pin! Whatever is interfaced to these pins must provide a logic low.
Tomorrow I'll post the actual code in VB 6.0.
@ GREG, Ron - tech gave you some good advice as to how to interface the phone line.
Ron