Hi Manny, try to think of elecrical impulses as light, because that is exactly what it is. Our phone lines are just a medium to tranmit light. If I point my flashlight at you at the exact same time that you shine your flashlight at me, we both see each other in the dark. When we talk face to face we transmit and receive at the same time. This is because we have built in drivers(Voice) and built in receivers(ears).
Thanks