I inherited an earthquake sensor (installed on a mountaintop) that has an analog output. Basically, when idle it produces 0v, but when there's motion it will swing between a max of +5v and -5v. The problem is getting the voltage info back to our classroom.
The system this came out of used a drum recorder in the classroom end. It worked over an analog dedicated 2 wire phone line, which I also have access to. The original system had a circuit (which is long gone) that would produce a 1000hz tone on the phone line when the sensor voltage was 0v, drop the tone to around 775hz on -5v and bring the tone up to around 1270hz on +5v.
At the receiving end, there was another circuit that did the opposite. ie. the audio tone would be converted back to +5v/-5v voltage and drive the drum recorder.
I am seeking advice as what would be the best way to duplicate the function of this circuit or even if that is the best choice. I also have a network connection to the mountaintop available, so I could probably put this into an A-D converter of some type.
The system this came out of used a drum recorder in the classroom end. It worked over an analog dedicated 2 wire phone line, which I also have access to. The original system had a circuit (which is long gone) that would produce a 1000hz tone on the phone line when the sensor voltage was 0v, drop the tone to around 775hz on -5v and bring the tone up to around 1270hz on +5v.
At the receiving end, there was another circuit that did the opposite. ie. the audio tone would be converted back to +5v/-5v voltage and drive the drum recorder.
I am seeking advice as what would be the best way to duplicate the function of this circuit or even if that is the best choice. I also have a network connection to the mountaintop available, so I could probably put this into an A-D converter of some type.