TAJS-C:
. . .I'm doing a project, and want to communicate manually to my arduino from long distances.
It's essentially working on a project with telephone lines, and I would like to be able to identify when somebody manually sends basic 1/2 second pulses of Negative voltages of more than -12V up to -50v in order to change the state of the arduino.
. . .
Can you clarify what you are attempting to achieve by this.
You have no explicit control over the voltages on a standard telephone line.
There is an on-hook voltage of approx. 48 volts DC
There is an off hook voltage of around 8 volts DC
There is a ring voltage of about 90 volts RMS AC 20 Hz
These parameters can vary depending on the country.
If you are attempting to send information via a (POTS) telephone line, you have to look at some method of sending audio encoded data maybe using DTMF or AFSK or similar.
If you are making connections to the telephone line and resistors are getting hot, you are definitely doing something wrong and you will risk impairing the normal function of the telephone line.
Edit: The voice channel is of the order of a few 100 mV