6v6gt:
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
Don't worry, the end-device is to be designed to assist line engineers fix faulty circuits- so the current status of the line does not matter.
This is why I'm trying to avoid going into detail about it being a telephone line- i'm essentially just testing the copper pair, and wanted a way to easily send a basic code down the line towards an arduino. By "tapping" the line on and off a few times- instead of relying on a GSM module or suchlike (Although LORA interested me very much!).
This is just a basic function of the device.
I'm simulating the entire thing in my laboratory, it's not actually a real approved device- just a proof of concept for a project.
I'm a telephone engineer, who is a part-time degree student.