The Transmitter: the transmitter lies behind the mouthpiece and it serves an "electric ear". it has an 14 eardrum as a human thus it is quite sensitive. The eardrum of a telephone is called the diaphragm, a thin round metal disk. As voice or sound waves entering the phone hits the diaphragm, it vibrates at various speed, depending on the air pressure and the speakers tonality. This allows the for electric currents to flow through as you speak and voices can be heard fromt he fluctuation of this current.
The Receiver: the receiver acts an "electric mouth" with vocal cords connected to the diaphragmn as electrogmagnets. it is made up of a coil or wire around it. When electric currents pass through the coil (duplex coil), the iron core becomes magnetized which in turn results a vibration in the diaphragm. As the diaphragm moves it pushes air pressue that sets up sound waves like the ones being sent into the the transmitter. The sound waves then can be heard by the listner.