MONOPHONE if put together in a handset :)

The word Monophone has been misunderstood by many. Some use for a whole telephone set.
But here is what existed before the transmitter and receiver were combined into a hand set.

If it wasn't for the MAGNET, we would not have had the telephone.

In Alexander Bell's primitive telephone, the double electromagnet was replaced by a single permanently magnetized bar magnet having a small coil or bobbin of fine wire surrounding one pole, in front of which a thin disc of iron was fixed in a circular mouthpiece. The disc served as a combined diaphragm and armature. On speaking into the mouthpiece, the iron diaphragm vibrated with the voice in the magnetic field of the bar-magnet pole, and thereby caused undulatory currents in the coil. These currents, after traveling through the wire to the distant receiver, were received in an identical apparatus. This design was patented by Bell on January 30, 1877. The sounds were weak and could only be heard when the ear was close to the earphone/mouthpiece, but they were distinct. WIKIPEDIA