Thank you for your answer but as far as I’m concerned what is transmited over the phone lines are electromagnetic waves. The sounds of the voice which are sound waves are converted into an AC current once you speak into the mouthpiece or microphone of the phone. This is done by the electronic circuit inside the phone.This goes over the phone line as an AC current modulated by our voice and it is analog not digital. The phone by itself does not convert from analog to digital since it is not a modem.This signal is not light because you can’t transmit light over a copper wire. You transmist light if you are using a fiber optic cable which is not our case.
If I think of this electric wave going up the line an the other going down at the same time, they could collide with each other someplace in the line.
I know it is a little difficult to explain and I’m pretty sure there must be some physics involved in trying to explain what really happens inside the wire
Thank you anyway.