The resistance is determined by the length and gauge of the cable conductors.
Keep in mind this low cost microphone element is designed to survive years of close proximity spitting and shouting as well as the occasional drop to the floor. Hybrid systems that are included inside telephones that are completely inside well insulated case used cannot thesis any electronics component in telephonethe hybrid circuti can be a non-isolating type. The ring signal is much the same, worldwide.
If electrical noise from an appliance leaked on to the wires somewhere between your phone and the phone company. It would be a really good thing if telephone tones were standardised throughout the world. While digital telephone lines are quicly coming to the telecom field, it seems that analogue telephone lines are still here to stay for a long time.
The importance of this characteristic impedance lies in the fact that if any length of line is terminated in an invention cell phones essay of this value, then all the energy flowing along the line is absorbed at the termination and none is reflected back along the line.