How can I get my PC to detect my driveway alarm? 12v detection?

[RichTJ99]

Hi,
 
I have a driveway alarm that is hard wired to a pico speaker in my house, the speaker makes a buzzing noise when it has power, which it only gets when the driveway alarm goes off.  I have a speaker that beeps when a car drives over the alarm.  I also have an Insteon door sensor that is set to send an email through the ISY when someone drives into the driveway.
 
I want to take the two wires from the speaker & daisy chain them 'somehow' to a computer so when the speaker for the driveway alarm goes off, the PC could detect the 12v dc signal then I could have it play a MP3 recording of the driveway alarm sound through the home audio system.
 
Is there some sort of USB device (or serial) I could use to detect the voltage change (from none to something), then make it play a mp3 when it 'senses' the voltage?
 
Thanks,
Rich
 

 

[jay]

I am doing this with 2 driveways using Homeseer and X-10.
My speaker is 12VDC at full volume. I soldered a pair across the speaker and connected to a PUM01 (X10.com) Powerflash Alarm Interface.
Position A accepts inputs of 6-18VDC. I set my house and unit codes and created events to announce arrivals and departures and on which drive.

 

[JimS]

You could hook the 12V line directly to one of the serial handshake lines and monitor that with software to play the sound. 
 
Here's a different application that used the handshake lines and some perl code (link is in the comments) for Linux.  That might be a start if you want to do some programming or give you an idea.
 
http://jimlaurwilliams.org/wordpress/?p=1556
 
 
An Arduino board could take the 12V (with appropriate resistors for dropping the voltage) and provide a trigger via USB.