The first telephone

Alexander Graham Bell
Alexander Graham Bell is the inventor of the first telephone and received his first patent in 1876. There have been hundreds of lawsuits for copyright but none have been successful. While he was a teacher for the hearing impaired, he was asked by a group of investors to perfect the perfect harmonic telegraph.
A telegraph is a system for transmitting messages from a distance along a wire, especially one creating signals by making and breaking electrical connection. Bell was set on creating a voice transmitting device. On March 7, 1876, Bell was awarded a patent on the first device and 3 days later called his assistant and electrician, Thomas Watson. The famous words were: "Mr. Watson, come here. I want you."

https://www.history.com/topics/inventions/alexander-graham-bell

 How it was made
Bell and Watson were working on a harmonic telegraph. When a reed struck on Watson's transmitter an intermittent current was converted to a continuous current. Bell was able to hear sound on his receiver confirming his belief that sound could be transmitted and reconverted through an electric wire by using a continuous electric current.

The original telephone design that Bell patented was a modified version of a telegraph. The primary difference is that it could transmit sound. Two years later he created a magnetic telephone which is consisted of a transmitter, receiver and a magnet. The transmitter and receiver each contain a diaphragm which is a metal disk. During a phone call, the vibrations of the callers voice cause the diaphragm in the transmitter to move. This motion is transferred along the phone line to the receiver. The receiving diaphragm begins vibrating thus producing sound and completing the call.

Drawbacks
Callers had to shout to overcome noise and voice distortions.
Time-lapse in the transmission.




Solution: The first phones contained a single microphone.
Thomas Edison introduced a model that had a movable listening earpiece and a stationary speaking tube.





Phones nowadays
Telephones still work on the same basic principles. The person picks up the handset and this causes the phone to connect to a routing network. When the numbers are pressed on a touch-tone keypad, signals are sent down the phone line to the routing station. Each digit is recognized as a combination of tone frequencies. The specific number will be sent to another phone and cause it to ring. When the phone is picked up, a connection between the two phones is initiated. The mouthpiece acts a microphone and sound waves from the users voice cause a thin, plastic disk inside the phone to vibrate. This changes the distance between the plastic disk and another metal disk. The intensity of an electric field between the two disks is changed as a result and a varying electric current is sent down the phone line. The receiver on the other phone picks up this current. As it enters the receiver, it passes through a set of electromagnets. These magnets cause a metal diaphragm to vibrate. This vibration reproduces the voice that initiated the current. An amplifier in the receiver makes it easier to hear. When one of the phones is hung up the electric current is broken, causing all of the routing connections to be released.

Materials
Range from glass, ceramics, paper, metals, rubber and plastic. 
Primary components on circuit board are made of silicon. 
Outer is made of a strong, high-impact resistant polymer.
Speakers require magnetic materials.
http://www.madehow.com/Volume-5/Telephone.html